I agree Barbarians are the most useful, because they have the most strength and can hold two weapons, but I explained a long time ago making mules all of the same class limits your space and time.
I made seven mules each account in LS2, with the eighth character being the play character. I would enter and exit a couple of times, building the time restriction up to around ten minutes coming in with the last mule, and would level him/her until I was safe. All my mules were CLvl12 so as to wear the piles of set rings I'd find (lots of Cathan's Seals and Angelic Halos), but I made the mistake of giving them generic mule names (NTTGO-One for New2TheGame1 mule number One). I fixed that this year by giving them real names and am in the process of leveling as many to CLvl31 so as to carry tons of gold. The extra character, however, is a Barbarian, but with a generic mule name I'll feel free to delete if I need to make an eighth real character.
It's just a matter of practice and getting to like certain builds. When I write that all-Paladin guide, assuming I'm still online, it'll show you only need four characters to do it every season, saving more character space to play Werebear or other Paladin designs, and even other class designs.