So why do I try?

[Cohen]

I'd agree with Skolem about the replacement.
Since you're the major power, and for what I've seen you're bashing your enemies.
Even with some loss.

I've tried Pyth in single player, and I've had the same problem ...

Simply Shaman isn't so good to cast relief after having casted Comm Master.
The AI seems to be scripted to cast any buff he can before anything else.
So a communioned Shaman get astral shield, astral weapon, protection/barskin, etc etc ... wasting a huge amount of turns in casting buffs only.

I believe however communion is wonderful, and allows you to cast spells that usually you can't.