1) Requires two feats for every metamagic you want to DMM with (the metamagic itself, and DMM for it);
Rather, it requires exactly 3 feats - extend, persistent and DMM (persistent). [Or quicken, if you prefer - also pretty effective, although not quite as effective]
And, with this one-time investment, you can pretty easily DMM 2 spells.(4 with extend/persistant)
2) The really abusive metas eat up slots (and thus turn attempts) like a Tarrasque (Persisted Divine Power is scary, sure, but it eats up seven turn attempts - one for activation and six for persisting. Undoable without wasting a feat slot on it, Nightsticks or a REALLY high Charisma, assuming point-buy);
So what? Mid-level, nightsticks are cheap, and then there is always the undeath domain.
3) A good deal of metamagic feats assume usage with damage-dealing spells, which the Cleric won't really be getting until 5th level - but the real kicker when using metamagic to great effect is to apply metamagics to spells that are pretty good to begin with, such as enervation, which deals negative levels rather than damage.
I disagree - the most blantant examples are not offensive spells, but rather buff spells DMM persistent.
4) Without DMM, some metamagic options just don't measure up to the real thing. Which would you rather have - maximized Cure Serious Wounds or Heal? (Just using an example.)
This is true, but you don't use metamagic on all spells ... you use it on the ones it augments.
Example Build:
Cleric 5 [planning, time] - feats: persistant, DMM(persistant), 1 free feat
- we have persistent extended haste and persistent extended mass lesser vigor.
- the entire party runs circles around enemies using hit-and-run tactics.
Example Build: -
Cleric 5 [planning, spell] - feats: persistant, DMM(persistant), 1 free feat
- persistent extended wraithstrike and persistent extended alter self.
This isn't overpowered? Even if you don't allow extend and persist to stack (which I think is raw), even with 1 spell, it is _very_powerful. And it just get's more powerful later on.
All of that said, I 1/2 agree with you. If we toned down the Persistant spell (so that it increased duration by a couple of steps, but didn't allow something like wraithstrike), and we made it so that it didn't stack with Extend, this would help. If we fixed some spells (alter self for example) that would help.
But even after all of that, being able to cast a maximized extended timestop or twinned maximized damage spells is still too powerful, in the sense that the cleric will be able to (a couple of times a day) insta-kill enemies which were supposed to be a serious challenge.
David