I'm just finishing a game with the Kuriotates, and it's real fun to have a 43 sized city... without discontent (and actually going to grow it more, puting one of my archmages with the law III level spell).
Fire magic is... the best. Playing on Prince, having 3 liches and 3 archmages making meteors rain onto the poor enemies that I have in front of me (including a civ such as the Ilians that are magic ressistant... you only have to amass more units to finish off the city) feels like playing in god mode, really (for some reason, the domination spell fails just too much for my taste...). All this playing on Prince difficulty. The key is not the main attack, but the collateral damage of... a LOT of meteors.
About the red dragon, I honestly don't know how to take it with axemen and archers, really... unless you have like 20 of them, and that makes worth it wait for upgrading. The IA is certainly not going to take him down until it has III-IV tier units.
I have played quite a lot of civs right now (most at Noble difficulty), and I must say the most overpowered were the Ljossafar. The Malakim also feel too easy, but only because of the creative-financial combo, which I feel still like the strongest at prince or lower level of difficulty, as in Vanilla civ.
The Khazad, with their vault thing, are quite fun to play, always having to make sure to keep a good stash of gold. But I guess the funniest game I have had was with the Balseraph. All special units, and all special indeed in a way. The next thing I enjoyed most was in a Luichurp game... I did not know the 'Barnaxus' effect, but when I found it... well, it was so handy to have an island with barbarians...
By all means, Kael & Co. DONT leave this... it's just too good. And it's only the first stage of a Beta!