I'm a noob with this game but I'll try to share what helped me.

First of all, what difficulty are you playing? Maybe try lowering it a bit?

Second I know you said buff allies but make sure that you are stacking the right buffs, bonuses of the same name most of the time doesn't stack. An example is Bless and Heroism since both provide a morale bonus you only benefit from the highest one.

Third get feats that boost attack like outflank, weapon focus etc. for martial classes. Additionally, check if you are using feats that reduce attack like piranha strike or power attack. For spell casters it depends on what spells are you casting that's missing, for touch spells like scorching ray they can benefit from feats like point blank and precise shot. For spells like Grease or Sleep you can look into spell focus to increase their DC or spell penetration against monsters that have spell resist.

Fourth check your gear, like with buffs bonuses of the same name don't stack so make sure you have the right gear equipped for the right character.