Bards weren't multi classed, they were three classed. They started play as fighters to a minimum of 5th level but could advance to 8th level. They stopped gaining fighter levels, dropped to 0 xp and started again as 1st level thieves. The only thing they could use from their fighter levels was their hit points.
Yes, and 3e "multiclassing" was the same as the dual-classing of earlier editions, except that you could go back and forth.
I deliberately used the 2nd Edition Bard as an example of a well done jack-of-all-trades class. Because it was. Unlike the 1st edition bard, which had to grow into its role, the second edition bard started out as a versatile character class. And, as far as I can recall, it worked very well. It was unique, but in my experience was reasonably well-balanced with the other character classes (within the somewhat looser "balance" requirements of 2e). Even when playing a bard as the 5th member of the classic 4-man-band (cleric, fighter, mage, & thief) adventuring group, you felt like a special snowflake, not a 5th wheel.
The bard was effectively a core class that had shades of a "multiclass" - fighter weapons, thief attacks and hit points, armor up to chain, decent access to magic, and a variety of special abilities to draw on - some of them duplicating those of thieves, but others unique.
The point I was making is that iteration of the bard class didn't seem to suffer from the problem of being either "weaksauce" or "overpowered" that seems to have played every jack-of-all-trades class since.
And no, it wasn't as powerful or unusual as being a bard back in 1e. But it also seemed a lot more viable to use.