with the knight, for the little time that i have him (before the next class upgrade) i now just equip him with 2 shields, front row, and defend every turn. And when other party members go into the yellow, he covers thier damage until he dies. So he is good for a good 8-10 hits on normal monsters, before i ever have to use a cure! But thats just my view, i think Jackal had a similar way too.

Samurai? Dont know, i think they took them out of this one.

No, there are no proficiencies in this, although certain classes can only weild certain weapons and armor.. IE warriors cannot equip rods or robes