I thought I would share my knowledge of the Death Guard and what I have learned about their standard traits, loadouts and equipment that you would typically see in a Death Guard Theatre of war.
So see below :)
Primarch: Mortarion, aka The Reaper
Previous names: Dusk Raiders
Homeworld: Barbarus (Destroyed)
Typical Strategic organisation: The Death Guard are heavy infantry specialists and therefore are quiet a slow force, but are able to withstand a punishing assault. They typically eschew Assault squads and favour Despoiler squads to clear out trenches and Zone Mortalis style environs (which they are the most experienced at throughout the 18 Legions). The Death Guard favour Vindicator Battle tanks when attacking an enemy position and are regularly used to "punch a hole" for Despoilers to pour through.
Armour traits: The XIV Legion favour the Mk3 suit for its hardiness and durability. Forces should be built favouring this variant. I use a ratio of 1 Mk2 / 3 Mk3 / 1 Mk4 in every 5 men.
Sergeants: Death Guard Sergeants do not use helmet crests. This goes with their "emblazoning and embellishment should be left to battle damage and grime to show my accomplishments" style attitude. Instead they make use of a single black Helmet stripe (see 'Betrayal').
Praetors: The Death Guard have 7 Captains (Mortarions favoured number), during the Great Crusade these are:
1st First Captain Calas Typhon
2nd Commander Ignatius Grulgor.
3rd Captain Ujioj - either 3rd or 6th Captain
4th Captain Ullis Temeter
5th Captain Holgoarg
6th Captain Unknown
7th Battle-Captain Nathaniel Garro
You can see my post Pre-Heresy Death Guard 7 Captains for pictures and images I have found of them.
Centurions: The rank of Lieutenant is used for Centurions (i.e.Lieutenant Crysos Morturg), there are many Lieutenants in each Death Guard Great Company.
Chaplains: The Legion does make use of Chaplains (see 'Distant Echoes of old Night' from Black Library).
Master of Signal: The Death Guard would use artillery or orbital bombardments.
Legion Champion: A Legion Champion from the Death Guard would probably be a Deathshroud Terminator (see 'Vulkan lives').
Vigilator: Not very fluffy
Librarian: The Death Guard do not have a Librarium during the Great Crusade, due to Mortarion's distaste for the Witch-breed, only during the Heresy do latent Psykers become Sorcerers in the XIV Legion.
Forge Lord: Every Legion will have a Forge Lord, he just may not appear much for the Death Guard.
Primus Medicae: Every Legion will have a Primus Medicae, the Death Guard do make use of Apothecaries in the novels (see 'Flight of the Eisenstein')
Siege Breaker: The Death Guard will assault straight against the walls which have been built to keep them out, just to prove there is no stopping the XIV Legion. Siege Breakers help with this (and lots of Vindicators).
Moritat: The Death Guard use Chemical, Radioactive, Nuclear, viral and Biological weapons against their foes. The Moritat is the master of this style of warfare and one is featured in 'Distant echoes of old night' for the Death Guard.
Legion Veteran Tactical squad: Every Legion has Veteran squads. When it comes to modelling these you need to know one thing; Dirtier and rustier the more battles this squad has seen. The Death Guard have, battle damage, dirt and grime as a badge of honour, it shows the conflicts the character has been through. Many will have personal commendations of cross Scythes from Mortarion to also exclaim their deeds. Heavy Flamers with Chem munitions and Missile Launchers are the fluffiest weapon choices for the squad for the XIV Legion.
Destroyer Squad: Very Fluffy, just don't take Jump Packs and walk in (see 'Distant echoes of old night") for true effect.
Terminators: The Legion makes use of both Cataphractii and Tartaros patterns of Terminator armour. Favoured weapons are Chem Heavy Flamers and some Reaper Autocannons. Combi-Flamers with Chem munitions are another good Fluffy choice for one or two.
Techmarine Covenant: All Legions have them
Apothecarion Detachment: All Legions have them
Legion Dreadnought Talon: All Legions have them. Would not make use of Conversion beamers due to how delicate they are.
Legion Contemptor Talon: All Legions have them. Standard Armament for a Death Guard Contemptor in the XIV Legion is Multi-Melta and Power Claw (see 'Betrayal'). Would not make much use of Conversion beamers due to how delicate they are.
Legion Rapier Carriers: All Legions have them. The Death Guard make use of them in trench warfare and sieges.
Deathshroud Terminator Squad: The personal guard of Mortarion, as well as a stand alone unit, this squad excels at getting stuck in in the centre of big masses of Infantry. Their shredding Hand Flamers and sweep attacking Power Scythes make them a good choice.
Legion Tactical Support squad: The backbone of the Death Guard Legion. Squads of 14 or 21 (with Apothecary / Lieutenant) are fluffy size wise Legionnaires are the standard (multiples of 7). They make use of Despoiler squads with Boltguns almost as standard, this is due to Mortarion's belief that a Legionnaire should be equipped to deal with any situation that he might encounter. Sergeants have varied armaments.
Legion Assault Squad: They have them but are only deployed when situation demands it. You will not see these in a standard Death Guard force.
Legion Breacher Squad: For a Legion known as King of Mortalis, the Breacher siege squad is a common site on Battlefields and boarding actions. Mk3 all the way. Try to hit the magic number of 14.
Legion Tactical Support Squad: The Legion make use of Support squads in many flavours. They typically eschew weaponry that is prone to failure or requires a lot of maintenance (goes with their ethos of durability). Weapons like Volkite Chargers will not be seen in the hands of the XIV. Meltaguns, Plasma guns and Rotor Cannons are standard whilst Flamers with Chem munitions are popular sights. Try to hit the magic number of 7.
Legion Reconnaissance squad: The Legion will have them, but you will not see them in a standard Death Guard formation.
Legion Land Speeder squadron: The Legion will have them, but you will not see them in a standard Death Guard formation.
Legion Javelin Speeder squadron: The Legion will have them, but you will not see them in a standard Death Guard formation.
Legion Outrider squadron: The Legion will have them, but you will not see them in a standard Death Guard formation.
Storm Eagle: The Legion makes use of them, but typically you will not see them. The legion prefers to land and meet their opponents on foot, braving their defences to prove their toughness.
Legion Seeker Squad: The Legion will probably not make use of them.
Legion Attack bike Squadron: The Legion will have them, but you will not see them in a standard Death Guard formation.
Legion Jetbike Squadron: The Legion will have them, but you will not see them in a standard Death Guard formation (much to my disappointment as I really like them).
Tarantula Sentry Gun Battery: The Legion will have them, but you will not see them in a standard Death Guard formation, but you will see them in a defensive strongpoint.
Heavy Support Squad: The Legion make common use of Heavy Support squads, this is evident in their Rites of War (see 'Massacre'). They typically eschew weaponry that is prone to failure or requires a lot of maintenance (goes with their ethos of durability). Weapons like Volkite Culverins will not be seen in the hands of the XIV. Missile Launchers, Plasma Cannons (see 'Horus Heresy card game') and Autocannons are standard whilst Heavy Flamers with Chem munitions are popular too. Try to hit the magic number of 7.
Legion Spartan: Owing to the durability and dependability of this tank, they are a common site.
Legion Vindicator: The Death Guard have in their possession a large amount of Vindicators (see 'Betrayal'), they are commonly used as frontline support for the infantry.
Legion Sicaran: Commonly used for the Traitor Legions from early m31. This is down to Horus Lupercal's forward planning and issuing them primarily to his allies.
Legion Predator: The XIV made use of Predators with Chem munition Inferno cannons. Would not make use of Conversion beamers due to how delicate they are.
Land Raider Phobos: The XIV Legion will make use of these tanks.
Land Raider Proteus: The XIV Legion will make use of these tanks.
Land Raider Achilles: The XIV Legion will make use of these tanks.
Whirlwind: The XIV Legion will make use of these tanks.
Scorpius: The XIV Legion will make use of these tanks and did so at Isstvan V.
Basilisk: The XIV Legion will make use of these tanks.
Medusa: The XIV Legion will make use of these tanks especially with Phosphex shells.
Caestus Assault Rams: The XIV Legion will make use of this flyer due to its durability and reliability. They were featured in XIV colours in the Betrayal book too.
Deathstorm Drop Pods: The Legion will have them, but will not use them as part of their standard deployment.
Grave Warden Terminators: Another Legion specific unit. The elite of the first company are called the Grave Warden, they specialise in chemical warfare and pack grenade Launchers. I plan to have enough of these to accurately represent a formation with Typhon.
Lords of War
Fellblade: The XIV Legion make use of these tanks at Isstvan III and Isstvan V. They are a popular Super Heavy for the Legion.
Typhon: The XIV Legion make use of these tanks at Isstvan III and Isstvan V. As they are based on the Vindicator design they get a lot of use in the XIV.
Glaive: The Legion will not make much use of the Glaive due to its delicate Volkite weaponry.
Cerberus: The Legion will not make much use of the Cerberus due to its delicate weapon systems.
Legion Malcador assault tank: The Legion will not make much use of the Malcador but will have some. It is too fast for the Legion.
Thunderhawk Gunship and Transporter: All Legions make use of them.
Mortarion: Enough said.