Whoa, I never knew about the "pick nose" trick, I've played thru the game a number of times as thief, both the original EGA and the VGA remake.
IMHO, the thief was the best class, the only one where you could get all the skills. And that's only if you started on QfG I. Starting as any other class, or a thief in later versions, and at least one of your skills was a zero, which meant you could never use or improve it (as far as I've ever found out).
That's indeed what I remember as well, but in at least one of the sequels it made sense to transition to a fighter to gain the paladin powers on top of the rest. Playing for maximum freedom was actually incredibly constraining in certain ways; I vaguely recall that you get forced by class into a specific endgame for Trial By Fire.
I have to mention to anyone who stumbles across this comment that there have been remakes. The QfG1 remake in 1992 was okayish, but I personally preferred the 16-color version in all its limited glory. But the QfG2 remake in 2011 was worthy of multiple replays just like the original was:
QfG3 is still playable via DOSBox if you can get a copy of the software. I want to play QfG4 again and I unfortunately have never played QfG5 as it landed when I was broke... but I did get a copy of the soundtrack via some filesharing network at the time, and Chance Thomas's work on that soundtrack was absolutely gorgeous.
IMHO, the thief was the best class, the only one where you could get all the skills. And that's only if you started on QfG I. Starting as any other class, or a thief in later versions, and at least one of your skills was a zero, which meant you could never use or improve it (as far as I've ever found out).