They weren't meant to be. I was pretty much like the A-Team, but before the A-Team.
Like everything in life from construction to surgery, you need people able to perform different things. If you can find one person to fill two jobs then great, but you had to decide what jobs you needed done and get together to perform a working group.
You didn't need Murdock there to fly because Face could, but it was a heck of a lot easier when he was since he was better at it.
Love the example - my son is currently going through A-Team episodes on our Netflix through the Wii. Ahhh, memories.
I agree with you though, there was never supposed to be a balance. If you played the game by the rules, getting a 1e/2e Wizard to survive through the early levels was punishing at best. That coupled with a higher XP per level requirment made it a welcome relief when at higher levels your power seemed to eclipse other players.
3e tried to change that with balanced classes and balanced XP progression. Great idea...on paper. However, their balancing changed lot s of things. Druids in 2e were tricky to play anywhere but outdoors to limitations on their spells - it was a limiting factor of the class IMO. In the wilderness however they very much owned the place. Now they are like the Swiss Army knif eof classes. Clerics didn't have near as many personal "buff" spells nor did they have access to spells like "summon monster" and as many direct ways to damage foes. They were more pigeon-holed into their healing role (Which was deemed a bad thing, and which consequently helped give rise to the end of co-operative party gaming IMO - no class had to fulfill a role and every class that could cast spells somehow needed to be able to do everyone elses job all of a sudden to be viable. Meanwhile the non-spellcasters were left in the dust).
Wizards were powerful, but did not have near as many options to override what were usually poor physical stats, whereas now in some instances a Wizard can provide an effective "fighter" substitute. And we can't forget that only fighters could have the really big Constitution bonuses to hit points and they had access to ther own "exceptional" strength chart.
The 3e attempt to balance everything placed power solidly in the hands of casters. They become necessary for a non-casters continued existence at much earlier levels. So again, on paper it was a "good idea" but execution didn't fully pan out.
So yeah, they weren't every really balanced, but honestly, I found more balance in 2e than 3e as far as classes are concerned. I know I have argued for the continued usefulness of a fighter as a class, and I feel it is not dead, but I do recognize other's arguments that at higher levels it becomes heavily reliant on spellcasters and magic to maintain viability. Of course, if your group isn't sold on the "well I can make a PC that does everyone else's job" idea then that non-caster can still have a place.
All that said, I do agree with the other poster's assertion that 2e is more simple system for someone to learn in some respects, but that ease does rely on a lot of ambiguity that 3e sought to exorcise (which in turn added more rules complexity).