Remove the skill XP limit, allow people to level up all their spells as they'd like, and make build choices (ranged vs melee vs single target vs AoE vs crit vs zerk/etc) be the way in which people define themselves, and from that choice, they then will use all their skills differently. You still know that the niche ranged Sacrier is going to focus assault, rejecttatoo, motion sick and lightspeed, but that's four skills you have to worry about from that one element alone, not to mention them able to now also throw rocks for good damage, or colonnades. And this should only scare you if you're afraid of people having choices--and you shouldn't be, because that's what makes shit fun.
This game is very, very slowly getting pushed in a better direction, but holy fuck is it like trying to push a boulder up hill. And TBH, they only have themselves to blame for any decline in popularity that comes as a result of them being so fucking slow to update, to finish content, to bug fix, to overhaul things repeatedly.. but seriously, this is something everyone knew was a bad decision when they implemented it.