At the start concentrate on Physical Damage for non Mages. As the game progresses and you start to get sets of 6 equipment that allows your hero to keep some of the morale then add Skill damage. Mages should have Magic attack first and Hit Point next for attacking.

For defense Dodge is the most effective rune followed by increase Max HP.

There really is no difference on the runes that you use by hero type other than Mages and non-Mages.

A tank is one that you concentrate on defensive runes and equipment upgraded. It does not have to be any specific kind of hero, but Cavalry usually works best. My main is an Archer and I have him build up as a tank and it works very well. It allows me to have more attackers.