To this point, the three attack types would be appropriate: Slashing, Blunt, and Piercing. Robots would be pretty resistant to slashing and piercing except at the joints, so archery likely wouldn't be the choice method of engagement.
Really, a robotic enemy would probably be considerably more resistant to almost any attack than your average human target, aside from in certain joints or wherever, but would also be less flexible/agile and more predictable. It would be a completely different experience to fight, which is what I'd ultimately hope for in dramatically different enemies.
Good points there, I'd do away with the "damage health" spell really, it could be replaced by something actually physically affecting you like a spell that causes blood to dissolve (some poisons do that).
What I replaced it with was a "kinetic force" spell, to replace it as the "non-elemental damage" type of destruction spell. I suppose people who absolute must have the classical elements could consider it wind. Higher magnitudes would increase the momentum of the spell force and subsequently its damage, similar to a weapon system that calculates damage based on the momentum/resistance in a weapon strike instead of a flat number.