Tessarael
Adventurer
Eldragon said:They tend to gravitate towards clerics... a lot. Mostly because they are considered the "best" class (understandably). With the proper combination of buffs, these clerics easily surpass the party fighters and barbarians in damage dealt. [..] In short, I need to give an incentive for 3/4 of the players to NOT be a cleric for once.
Common opinion is that Clerics are overly powerful as you noted. I would drop their BAB to 1/2. That makes it much harder for them to be a good tank. (I'd still be inclined to leave Druid BAB at 3/4, as Druids are intended to be able to tank and Druids get less spells. Unless you have a problem with them playing Druids ...)
Now, if they're buffing themselves, why aren't they buffing the party tank? That has got to be more effective, unless those spells can't be cast on the tank. Consider changing spells like that to allow them to be cast on another person (range touch). This at least will make 2 Clerics and 2 tanks a better combat party than 4 Clerics.
Hiring NPCs should be far more difficult at high levels. There simply aren't that many high level Rogues, Wizards, etc., that aren't doing anything better in their free time.
Don't allow spells to replace needing a Rogue. Get rid of Find Traps, Jump, Knock, Spider Climb, and so forth. Those are the main spells that spring to mind. Clerics don't get many skill points and if everyone picks Cleric, the party simply can't handle a wide range of skill situations. Require Listen and Spot checks with high DC sometimes - that requires a Druid, Monk, Ranger, or Rogue for Spot; Barbarian and Bard also get Listen. Similarly for other skills - e.g. situations where Bluff might be useful.
Combat-wise, Clerics need time to buff. Don't give them that time always. A typical combat lasts 3 to 8 rounds. If you spend 2 to 3 of those rounds just buffing yourself, you're taking damage and not damaging the enemy. For encounters that they are aware of ahead of time, no problem, let them buff. But sometimes they can be ambushed, and then they will be in trouble. Enemies should use Silence to stop them spellcasting. Dispel Magic will help remove their buffs. (The way we rule Dispel Magic is that you roll separately vs. every spell in the area of effect, so a Dispel Magic can really rip through those buffs they'd prepared.)
Just my thoughts ...