AA has a great post immediately above which answers most things, so I’ll just throw a few supplementary words out.
Absolutely. Bigger and broader guns (hirelings and companions or squads of them) in order to offset Wizards ridiculous inherent scaling.
I think the REAL problem with 'classic D&D' style casting is the vastly greater PLOT POWER of the casters. It isn't that they're incredibly more effective in combat. Heck, my 14th level AD&D wizard was NOT actually THAT much more potent at just plain killing targets than the swingy types (well except the thief, but that's a whole other story...). Yes, he might, now and then SOD off a whole fight or something, but truthfully that kind of thing is problematic at best. There's a good chance Mr Monster has MR, makes his save, your clever off-label spell use gets nixed, a kobold knicks you in the shin with a stray dart while aiming at the thief, etc.
No, what made the wizard so dominant was the whole question of how MANY different approaches to a given operational challenge he could employ. Frankly "Questioner of all Things" wasn't blasting stuff to bits that much. His entire spell loadout was oriented towards having 'that one spell' which was going to make the difference somewhere down the line. I had a good solid 100 scrolls too (and a portable hole to carry them in). If I had to get down and dirty and FIGHT, that's what Staves of Power are for...
A lot of those spells might be used to gank or incapacitate foes of various sorts, its D&D after all, but often it was the teleport, the improved invisibility, the polymorph other, fly, or wall of stone, that did the trick. Often whole adventures would be BUILT around "When we get to the stairs Questioner will cast..." You wouldn't really get the same plot traction as a fighter. If the action didn't basically involved "and then we kill it" there really was no call to plan around the fighter beyond "if we run into some bad guys they'll chew on my shield instead of your leg and then I'll dice them into small bits." VERY HANDY, but you can hire cannon fodder who can pull that off. Try hiring a wizard to cast spells for you!