Is the insane damage output of rogues your main concern?

This change would have a large effect on game balance and should be considered carefully before being implemented. Making it self-cast only and removing pills/potions/herbs would pretty much remove it from the game, since shamans/priests don't have much use for it in pvp.

This would nerf: rogues, scouts, mercs, and maybe swashbucklers. Of those classes, rogue is the only one that might require any kind of nerf.

It would also keep people from using it as an aggressive spell against casters. I like the fact that this option is available, though.

Barb with fury is more damage than merc with frenzy. What are you complaining about?

I think mercs are fine as they are, though I have not done any testing with mercs and frenzy. My impression was that frenzy + specialize would allow a merc to approach the barbarian's damage output, but would never match it. I'm not sure I see why mercs should be nerfed. I could definitely see an argument concerning rogues, though. I think the main reason nobody complains about rogues is that they are usually played by idiots.