tenkar said:
Guess my experience with AD&D was that multi-class characters fell far behind the rest of the party around name level (9-10) as their THACO and HP were usually substantiallly lower. The fighter-thief doesn't tank as well (lower ac and hp) as a fighter of equal XP, tho the thief abilities don't lag all that far behind.
At the same experience totals, a 1e Ftr/MU (using the UA advancement rules) would be 9th/10th level, while their single classed fighter counterpart would be 10th level. The multiclassed character would have a THAC0 one less, and fewer hit points (the Ftr would have an average of 5.5 per level, through level 9, for a total of 49.5 + Con bonus, while the Ftr/MU would have an average of 37.25 + Con bonus), but on the other hand to offset these deficiencies, the Ftr/Mu would have
all the spells of a 10th level magic-user, which would more than compensate.
In 3rd ed, if my cleric takes 1 level of fighter for the bonus combat feats, or my wizzie takes a level of thief first for extra proficiencies, weapons and abilities it like getting a major free bonus at little cost. You are right tho', in 3rd ed it is a liability to try and keep more then one class leveling.
Your wizard or cleric loses an entire level in spell casting, undead turning, familiar advancement, and all of the other benefits of their spell casting class. In exchange, he gets a few skill points, or a few hit points, and maybe a bonus feat. It's generally not a great trade-off. By taking a second (or third) class, you dilute the abilities of your other classes.
Which would you rather be? A 4th level cleric/1st level Fighter, able to cast 2nd level spells? Or a 5th level cleric (able to cast 3rd level spells)? It depends on your situation, but one is not obviously better than the other. In the way a 1e Ftr/MU is better than a 1e Ftr.