Well, you don't need to get +3/+4 to every attack to be borked.
Take an example I pulled earlier in the thread.
War chanter spends AP.
Each ally within 5 gets +con/+con to attack and damage till end of your next turn.
That's every attack they make. Multiple attack rolls, AP actions, interrupt & opportunity actions, etc.
As premium as AP cheese gets.
The bard gets an extra action and not much else. Right?
Wrong.
Extra action on a war chanter = additional opportunity to grant those inspire by word temp hp (if you failed with first standard action).
If it happens to the the turn after you landed a guiding strike, it's one more action targeting a -2'ed defence ... which is not fantastic, but hardly nothing.
I also love half elf valorous bards ... not the least being for their access to action surge ...
Finally, if that AP'ed action (at an effective +5 to hit for said half elf bard) happens to be for Harmony of the Two (Bard 13, PH2) ... all your allies within 2 gets a basic vs that foe ... remember that they're getting +con/+con to thier hit/dam.
Now all this is scary enough, but it's a half elf bard war chanter.
They can pick up many MC feats, so MC warlord ... giving 'em access to avenging spirit feat.
War chanters can spend 2 AP per combat.
If an ally drops, avenging spirit gives them an extra AP.
Borked.