Not all clerics should be martial. Priests of Aphrodite are more likely to be nekkid than don armor. Some interesting deities are practically pacifistic or at least unlikely to wear armor or bash a skull in. Balance clerics as casters, first. If someone wants to play a divine skullcrusher, let them multiclass with fighter or open up paladin to all alignments and make it similar to the current cleric, just weaker with spells. I still think multiclassing would be a better choice, though.
Speaking of clerics, rework domains and spell selection so that the clerics of St. Cuthbert and Wee Jas feel a bit more different.
And, turn undead/divine channelling. First, remove the silly association with positive and negative energy. Wizards deal with cosmic forces. Priests channel their gods. Second, don't give turn undead to everyone. Make it a talent tree type of ability where someone may turn, someone else may smite, a third may get a strength boost. Better yet, dump it and tie it to something like a domain ability.