They are referred to as the Pyre Warden (may be Sslamanders). Now obviously this is one of the older designs we remember from the Rogue Trader era of GW (see below).
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I think it is a good homage paying modern design of this suit (which I cannot confirm the true name for), and if they are breaking through into the Horus Heresy Novels it is almost confirmation that FW will have to do them.
They are the Deredeo to the Contemptor chassis; a extra heavy weapon sporting Terminator squad. The lead has what looks to be an Assault cannon and Heavy Bolter whilst the one behind may have a Graviton cannon and Lascannon.
There could be a spot on my Shelves for them.