Against a Dwarf, you definitely need a tactic (attack), and it would be good to have fire resistance (light magic...). I think that, in general, the best way to fight a Dwarf is to use summoning magic, so if you're sure the Dwarf won't go into Chaos and you have access to the corresponding spells, you can try taking a Dire Elf...
It's also good if you manage to take out the archers (you can even use dragons for this), position Ents around the perimeter in a defensive stance, cover the other side with a summoned Phoenix using enhanced spells from new Druids, and clone archers for yourself... that way, you might still have a chance.