[Aerich]

With fighters, the extra weapon proficiency is gained on every 3rd level - so you will get another slot at lvl 3. Thaco improves by 1 for every fighter level gained. The # of attacks improves at lvls 7 and 13.

Dualing at lvl 7 can be a nice compromise between a fighter class and spellcaster class, because it only takes 64 000 XP. It slows down the spellcaster's level advancement a lot in the early game, of course, but it gives the caster a legitimate fighter's ability as well, once the levels are regained. Might not want to experiment too much on the first time round, though.