@arkandel Yeah, I'm not super familiar with WoT (just never got into it), so grain of salt as far as all this goes.
The first thing you bring up, well, it doesn't surprise me at all. Players getting around restrictions by trying to find edge cases and loopholes is as old as RPG gaming. The three ways around it are players who are willing to buy in to the spirit of the rules, arbitrators who are willing to shut down attempts to bypass them, or rules that explicitly disallow that sort of shenaniganary. (On a MU*, the first is basically impossible, just because most don't have enough of a screening process to enforce that sort of things.)
The second comes down to the "interesting choices" thing I keep going on about. Why, as a player, would I pick "not-wizard" over "wizard"? How is "not-wizard" something other than "the PCs who are wizards can do whatever you can, but also they are wizards and can get up to wizard shit."
If you want "not-wizard" to be regularly played, you need some good answers to that! Otherwise it gets to be like the oWoD games I mentioned, where even though vampires are supposed to be vastly, vastly outnumbered by the mortals, the assumption is explicitly that PCs are vampires and playing not-a-vampire is a niche option.
Also, yeah, more or less everything that @Pyrephox said. Novels don't need to worry about balance because it's by design that someone is just cooler and hotter and better than everyone else, that's why they get to be the protagonist. Even TTRPGs can be fine focusing on two to six of the specialist snowflakes in the world. When you get to 20+ players, things start to shift.
So asking about WoT specifically (with, again, stressing that I'm not overly familiar with the setting), I might well start by saying something like "you can't buy combat skills if you're a Channeler, maybe there are in-universe ways that someone could have but your PCs didn't." A little harsh, but sometimes you need to be. And/or maybe saying that magic can only be used in a scene with a runner, where the pitchfork mobs present a real threat. Or maybe a more FATE-style narrative system that doesn't bother with the physics simulator aspects. Something where in-universe the wizard can throw up walls of fire while the warrior has a knife, but mechanically they're rolling more or less the same "Overcome Obstacle" dice.