First, I love clerics.
Second, I want domains badly.
Third, I don't like the OPs stuff. It's too much.
Fourth, I say keep it simple. Access to spells and 1 MINOR ability. I think it should be more feat-like also similar to monk/fvs stuff.
The balance is that spells cost SP. Furthermore, clerics wouldn't get as many enchancements for domain spells. So a fire domain cleric would never overpower a fire savant, etc. A death domain cleric would never have the DCs of a palemaster. Need more balance? Increase cooldowns by 50% or something. That would be fine.