I'm as familiar with Cheater of Mystra style builds as you are (ok, maybe not, but close?)...
But those break the game at a point where it is already damned broken in favor of spellcasters, and persistant doesn't do much to change that. Honestly, if there's a level 13 cleric in the party and he wants to go swing like a level 13 fighter without feats? Go for it. Be my guest! Rather have him doing that than casting level 7 spells.
I know it's kind of unfair of me to define the game as broken in favor of spellcasters beyond level 12, but if we want to get into that, I think I can hold my own. I will concede anything you wish about Divine Metamagic being too powerful at high levels.
Let's establish the following:
1.) Up until Divine Power, persistable spells are mediocre at best. From levels 1 through 6, there's no chance that the cleric touches a fighter in melee, 'cause there's just nothing that's particularly good to persist.
2.) At level 7, tides change somewhat, because you can persist Divine Power. If you spend 40% of your character wealth (7,500 out of a recommended 19,000) on a nightstick, and you put a good stat (16) in charisma, you can persist Divine Favor as well. This nets you a fighter's AB, HP, and better strength.
Now. With this character tailor-made to exploit Divine Metamagic...You will probably end up fighting with a strength 2 or 4 higher than the fighter (unless you wish to spend time during each combat sipping a glass of chilled wine and buffing yourself while everybody else fights), 1 or 2 more points of AB, etcetera.
He has 7 feats and 7,500 gold, if he's a straight fighter, to make this up. If we decide to tweak that fighter for damage, he will quite simply lambaste this poor creation in terms of combat prowess. And if we tweak him for other things (battlefield control with spiked chain tripping and AoOs?), he will dominate combat in that fashion.
Understand: I'm not saying that Divine Metamagic is bad.
I'm saying that the tradeoffs you make (Undeath and Planning have really quite terrible domain spells, at least at earlier levels), and the feat expenditure, just aren't really worth the ability to be a fighter without feats.
-Cross