Yes, this requires new perks. For example: Warrior +1 hp per level + 10% attack( caped at lev 3 maybe),but the weakness spell damage, weakness should be. etc.

 In general it is better to add a specialization to weapons.  Assassin. It uses short swords and daggers. They should not cause a lot of damage, but ignore the part of the armor and the levels it should get better. If the new rule will be added to the tactical battles. Where 2-3 units get bonus damage when fighting with one, it will be interesting.

 We also need new weapons, armors. For doctors Staves - Regen Army and ability  heal, but the 20% weakness to physical damage. So you can create the actual classes. For mages also need things which give simple magic spells. And now it is not mages he alternative damage dealers.

 Sorry for the language.