That was one of my least favorite changes in PF1 for both the classes it affected, though for different reasons.
Barbarian: No. Rage should not be a spigot you can turn on and off as needed. Once you see red, red it is until your foes are gone.
Bard: A horrible nerf. 3.5 bards can use bardic music 1/day/level. For most uses, a single use covers a whole situation. Inspire Courage/Greatness/Heroics works for 5 rounds after you stop performing (so the whole battle in most cases), Inspire Competence would help for checks taking up to 2 minutes, Fascinate could distract folks for as long as needed, and Song of Freedom would let you cast break enchantment, one of the most powerful anti-condition spells in the game for a single use of bardic music. But in PF, each round you do a bard thing costs one of your 4+Cha+2/level rounds per day. You want to boost your allies in a four-round fight? That's four rounds. You want to help your rogue buddy take 20 on opening a lock? Well, there goes 20 rounds. Each round you want to keep someone fascinated is one round gone (not to mention that the save now uses a normal formula instead of the bard's likely ridiculous Perform check). And Song of Freedom is gone, replaced with the anemic Soothing Performance, mimicking a mass cure serious wounds instead of break enchantment and costing four rounds of performance. Blech.
