Thank you all. This was very helpful, especially the taunt/cover/guard combination, the class suggestions and the passive skill suggestions.
@ Boring Old Tarq
I hadn’t meant that they can’t use any active skills at all, but it does actually help to think of it that way. I want the lack of magic to be impactful, but not detrimental to the character. I won’t be giving them damaging abilities or active healing, although boosting the potency of items is an option.