I've seen many gunslingers choose Pistols, because the dual wield them and then take weapon cords and tieflings so that they can reload as a swift and juggle 3 guns. You could make Vital Strike a good option blocking swift action gun reloading, such that it becomes move action reload, standard action vital strike w/ musket for 2d12+x.

You could make Vital Strike better by making a move action more valuable. Many optimization minded players pick Beast Totem for their barbarians because it gives them two claw attacks, and then pounce, which is a dumb ability for a PC to have. Getting rid of this, and by not letting your player's barbs walk up to enemies weapons drawn during "diplomacy", and by making more mobile enemies and by putting furniture or undergrowth so that the barb doesn't charge-draw-rage-swing means that a standard is what you expect to get rather than a full attack. Make enemies that use dirty trick, necessitating a move action that clears the condition. Make enemies that don't run up to the PCs, but rather kite them so that the PCs need to use their move actions to move. The choice then becomes simple. Power attack, > Furious Focus > Vital Strike, giving that extra 7 damage on a standard rather than nothing at all.

You could get rid of Furious Focus as a feat. If players couldn't take furious focus and ignore the Attack penalty two-handed power attacks stop hitting. Particularly the 6+ BAB bonus attacks Then it stops becoming a "trap option" to make a sword and board fighter. Lets consider a tower shield spec fighter. They'd be less concerned with damage output and more concerned with increasing accuracy. Many people currently say "Oh, no, you always want to two hand furious focus power attack, and get your BAB bonus hits, highest damage and accuracy". But if all these power attacking barbarians were reduced to the same accuracy as a one handed, it stops being the trap option.

The shielded Battle Host Occultist, Battle Cleric, Warpriest, or even Fighter should decide that they don't actually want to power attack, because they don't want the decrease in accuracy, preferring instead to hit an enemy, drawing attention away from the squishy wizards. So, to increase damage output they will instead take Bastard Sword proficiency and Vital Strike, maybe even weapon specialization. With that extra move, they can do things: Move to their enemy (of course), Feint, Use Godless Healing (can get useful with this, Start a bardic performance, use Quick Wild Shape, a phalanx can grant cover, . Maybe there are other things you can do with a move. I think there are ways to get aid another.