My own experience is that wizards are not particularly overpowered; full casters generally are. Bards, clerics, and druids can dominate the spotlight just as easily.
Honestly playing to early double digit levels generally, out wizards have not dominated the game.
I think my issue is that they can make things too simple and can swoop in to do others primary thing.
I guess my answer about how to nerf wizards probably applies to situations in which the group thinks the wizard is making the game less fun for others.
When this is the case, what spell or combination of spells are the problem?
My own experience is that there's a few spells that
can end up solving an entire encounter with a single spell slot under the right conditions:
force cage can completely shut down a fight if there's only one enemy and they don't need to be killed; just avoided. Most such spells aren't that good unless the conditions are just right; if you need to actually slay the dragon
force cage just lets you get a short rest in before the fight begins which is cool but not dominating the encounter. If these kinds of things happen too often, the full caster can be a bit of a spotlight hog.
The simplest way around this is just have more encounters between rests; that will increase variety, make spell slots precious, and generally prevent full casters from dominating all or even most of the encounters. You can and probably should let this happen once in a while - that's Shooting The Monk for wizards - but you don't want it happening so often that the fighter has to wait a month before they get to hit anything with a weapon. But as we know just having more encounters is easier said than done.
But there's another observation here: sorcerers, despite being full casters, don't seem have this problem. Why? My guess is fewer spells known, which means they're less likely to take spells that do very specific things. They take spells that deal damage, because damage is always useful (but it doesn't hog the spotlight). So the "proven" method would be to cut down on the number of spells known/prepared to make it less likely that the perfect storm will come up, making it therefore more rare and special.
New rule: you can prepare a number of spells per day equal to half your level + spellcasting mod. No more domain spells for clerics.
(Although I still feel that just giving fewer slots per day will get the same result without being as much of a fun-drain.)
