[Nick_K]

Abysia are quite hard at first: you need to really take advantage of their fire immunity for them to be worth the cost, and their high resource cost is also a problem. Make sure you take productivity and order. Also, don't hesitate to convert your fire gems into gold with alchemy at the start.
The anointed are amazing battlemages. Script them with summon phoenix power then falling fires / fire cloud / pillar of fire. You can also use anathement salamanders which are recruitable anywhere. The dragon is not so good due to old age.
Abysia are also very good at blood magic.

Other fire nations can suffer a lot from friendly fire, and I don't think anyone has a battlemage like the anointed of rhuax. I think that fire is one of the rarer paths. Perhaps Marignon is the next fire nation after Abysia? I haven't played them in dom3 yet, but in dom2 they had a fire-3 mage.