Sure, he has 2 natural attacks that hit for d8+22, or maybe two attacks with an actual weapon that deal d6+33 and a bite that deals d6+11... A level 13 fighter with just regular Polymorph would have 3 attacks doing at least 3d6+20ish depending on his gear and a comparable attack bonus, plus the bite doing d6+5, and then all would benefit from Power Attack. If he power attacks for -5 then that's 3 attacks with a large Greatsword doing 3d6+30 and a bite dealing d6+10. Depending on the fight, his gear selection, and his feat selection, this damage could be MUCH GREATER (FBs would be especially scary), especially on a charge, and it's really not going to be worse at any point.
And the wizard melees for 3 swings, each doing 1d6+40 under the same conditions, and also bites for 1d6+16. And oh yeah, he's still a Wizard, with everything that means. Of course since the wizard has +32 to hit even without other buffs, and is attacking touch AC he can just PA for full... and while that's normally under 6, there's plenty of things that give full casting and > half BAB.
In other words, that fighter makes better use of your 4th-level Polymorph than your Wizard does of his 5th-level Draconic Polymorph and his 7th-level Bite of the Werebear, plus your Wizard would be able to stand back and cast a 7th-level spell that's actually, you know, GOOD.
No, the Fighter still fails, with or without Polymorph and the Wizard still wins, with or without Draconic Polymorph.
Base Attack Bonus is essential for something other than basic combat, if you recall. Many prestige classes require a minimum base attack bonus, and Wraithstrike will not qualify you for those.
Now if only there were more beatstick PRCs worth a damn, that might actually mean something. But there aren't, so it doesn't.
People whining and flailing about me aside, any party arrangement that does not include a fighter > any party arrangement that does. Even if the fighter does not replace anyone, and therefore the alternative is an empty slot. That means 2 GOD Wizards > anything and a fighter, 1 GOD Wizard and 1 Gish > anything and a fighter, and 2 Gishes > anything and a fighter. Both in terms of auto attacking for HP damage and overall being better. Why? Because fighter = The Load, and you are always better off without one of those.
I'm not sure what the fuck any of this has to do with armors heavier than light though.