Another CR/LA/ECL/EL rant, eh?
If you really want to tie yourself in knots, try explaining how adding a level of fighter to a monster makes it just as much more dangerous as adding two levels of outsider or dragon.
Straight up, 6th level LA+0 fighter wt. mundane weapons vs. 12HD outsider (no racial abilities, no class levels) and mundane weapons? Let's see...
BAB +6/+1 vs. +12/+7/+2
Base Saves: +5/+2/+2 vs. +8/+8/+8
Skill Points: 18 vs. 120
Feats: 7 vs. 5
Hit Points: 33 (avg.) vs. 54 (avg.)
So, I guess 2 feats are worth +5 BAB, +3 Fort save, +6 Reflex save, +6 Will Save, 21 hit points, 102 skill points, and assorted sundry benifits for having more HD. Those are some really good feats.