I run a game with 6-7 players. Most of those players do some form of physical attack with a wix of some spells. There is only one mage/sorcerer. The bard in the group uses discordant voice along with Inspire Courage now every combat. Those two are causing the game to start to become very lop-sided in favor of the PCs.
So first Inspire Courage is added +3 to every attack to hit and adding +3 to every damage roll for ALL players within 30 feet. +3 adds about 10% chance for every attack to hit. That alone is pretty pwerful. BUT< it also adds +3 damage to every hit (unnamed type that can't be countered). Taking my one character that gets 7 attacks a round with two weapons, and hi hits 6 out of 7 times (thanks to +3 to hit, he has a +18 I think to hit with all his feats, a +2 two-handed sword, etc.). So for one full-atack round he gets an additional 18 dmg on average just tacked on. Consider that his weapons are already +1d6 fire for his weapon and that adds up fast.
NOW, add discordant voice. This grants ALL PCs within 30 feet +1d6 sonic damage to every hit. For this one fighter alone, this will add between +6 and +36 damage each round! If you look at the average, it should hover around +21. So that's +18 for the inspire courage and +21 for discordant voice, for a total average damage of around +39 damage each round in addition to the bard having his own ability to do whatever they want during the round.
Now multiply that times 5 characters (giving them half the bonus because they are not fighters). For those other players, a melee round adds about +18 damage EACH. So, for the fighter and 5 other characters, that one feat will (on average), add +129 damage per round. At its MAXIMUM, it will add +220 damage EACH ROUND. On average, the one fighter alone does around 180 - 220 damage each round right now. Almost no 13th level monster can stand again him for one round with a AC under 35.
The ONLY wany I can stop this is to constantly control PCs using whatever crowd control I can have.
I thought of actually putting up a mirror party against the PCs (same basic powers), but it would just come down to two fighters and everyone else would be dead. Because if the fighter is next to you when the bard is singing and the round begins your character is gone.
I'm a bit perplexed on how to handle this without just escalating the baddies to all have inspire courage and discordant voice for every combat. This is feeling very much like the old haste, where is you didn't use it you basically get destroyed.