lans: Define "only uses Divine Power". Uses Divine Power as his only combat buff? Uses DP as his only spell, period? Uses DP as his only spell and other modifier to stats (to the exclusion of stuff like Knowledge Devotion or a magic weapon), period?
The claim was that it obsoletes the fighter, so just that spell. I don't have any illusions about a cleric not being better over all, or not being able to obsolete the fighter with Divine Power+other buffs.
Alright, I'll try. Let's give them a 32 point buy. Let's say the Cleric goes for a 16/10/14/10/16/10 spread, while the Fighter gets himself a 18/12/16/8/10/8 spread. Sound reasonable? I'll put both at level 7, the lowest level at which the Cleric has access to Divine Power without trickery, and disregard prestige classes. Each will put his level 4 bonus into their primary stat (This doesn't matter much, as it's only a +1). Both shall be humans, and I'll only outfit them with a +1 weapon and +1 armor each - specifically, each gets a reach weapon he's proficient with and +1 Full Plate with armor spikes.
Cleric 7
Str 16 [22], Dex 10, Con 14, Int 10, Wis 17, Cha 10
Feats:
Extend Spell (H)
Persistent Spell (1)
Divine Metamagic (3)
Extra Turning (6)
With Divine Power online, the Cleric has the following stats, assuming average hit points:
49 hp +7 THP (total 56)
AC 19
BAB +7/+2
Full Attack routine: +14/+9 +1 Longspear; Damage 1d8+10
Saves +7/+2/+8
Fighter 7
Str 19, Dex 12, Con 16, Int 8, Wis 10, Cha 8
Feats:
Any eight, four of which must be [Fighter] feats. Power Attack can be safely assumed, I think.
Again assuming average hit points, the Fighter has the following stats:
64 hp
AC 20
BAB +7/+2
Full Attack routine: +12/+7 +1 Glaive; Damage 1d10+7
Not exactly equal, but I'd say they're close enough that they can said to be nearly so. The Fighter can pick his feats and has the opportunity to Power Attack, as well as sligthly better AC and Hit Points, but the Cleric definitely has him beat on the offense (consider also that a lower attack bonus means you can power attack for that much less without compromising your ability to hit). So considering that the Cleric gets this base
plus domains (which may give him bonus feats, a better weapon, or other awesome abilities), and spells, I would indeed say that a Cleric using Divine Power can safely replace a Fighter (and thus obsolete him).