I'm thinking of what lists to try first and think that CoS got some pretty nice combos with the new edition, if i didnt oversee anyting from stopping them:
Hallowheart + Arcane Tome:
makes the bearer a wizard and hallowheart gives another cast. Could be nice on for example anointed on foot or phoenix to create a very tanky wizard with 2 casts.
edit: "Flaming Weapon: Casts on a 4+ and improves the damage of one of the casters weapons by 1. " Seems quite good in conjunction with the above to make phoenix more killy.
Actually, with the wording on the frost phoenix "This model can included 1 Anointed armed with a Great Phoenix Halberd. If it does, this model has the Hero keyword.However, if it does, any command traits or artefacts of power only affect attacks made by the Anointed."
Currently it should be possible to use flaming weapon on the phoenix talons, as it is neither command trait nor artefact, which would be insanely good and probably not intended. Still very good to buff up the hellbeard attacks and get an easy proc of the + save for phoenix.
2 gyros in grand battery core battalion:
Gives a free Unleash hell, which might be quite nasty on gyro actually, as after the charge probably quite a few foes are in range of the steam gun. Also pretty hillarious imo!
Super tanky phoenix stuff:
Frostheart Phoenix can Heroic Recovery every herophase, which heals on average 1.6 wounds per phase. Normally not very killy, he can use stomp for mortal wounds or roar to disable command points. As healing is generally great value on the phoenix, i think he will be super obnoxious.
For phoenix guards it might still be worth it to run a big blob of 30 and try to get rally off, which is pretty awesome value on these guys. Might be too expensive though. Also a very good target for the hold the line objective.
Did you find any other nice combos yet?