This game has defeated me. Oh, I'll still play to at least 20 hours (if Bad Rats couldn't stop me, I imagine nothing will), but my dream of becoming the greatest mage in the realms is dead. I managed to beat Mulahey, thanks to Imoen's wand of magic missiles, but that still wasn't enough to bump me up to level 2, and after that, it was more or less one humiliation after another. The straw that broke the camel's back was Zal, "the fastest dart thrower in the west." I took out his partner, Vax, easily enough, and then he proceeded to wipe out my entire party.
To be fair, thanks to a quirk in the rules of AD&D 2nd edition, a high strength fighter specialized in darts is actually one of the strongest low level builds, and it's more than a little funny that the makers of Baldur's Gate referenced this absurdity in the game, but nevertheless, it is not at all fun to be on the receiving end of such cheese.
So, I started over, and built for survivability. I'm playing a half-orc fighter with max physical stats. Thanks to weapon specialization and armor, I'm now soloing encounters that used to wipe my entire party, and because I haven't recruited any npcs (and dismissed mandatory party member Imoen - I hope like hell that doesn't come back to bite me in the ass), I'm now level 3. My plan is to continue fighting random monsters by myself until I reach level 5 and then recruit a party. Hopefully, I'll be able to then snag a spellcaster with level 3 spells and enough hit points to not instantly die, and the fighter types will be accurate enough to actually hit the enemy more often than not.
I think this will work, and that I'll actually be able to get to the end of the game this way. I just wish I could have done it as a badass arch-mage (speaking of which, I noticed a bug - when you play a specialist mage, you can memorize any spell in your extra slot, by the rules you should only be able to put your specialist school spells in that slot - I wonder what other ways my knowledge of AD&D's rules might be screwing me over).