I agree with this assessment of incarnate spells. The only reason this is a summon spell, in pathfinder, is because you called it a summon spell. Due to it's inability to be interacted within any manner besides dispel, just makes it a spell with 2 effects. One in the first round, another in the next round. I am fine with that type of spell, but it isn't a summon. At least not a pathfinder summon. Just call it incarnate and take away the thought that it is analagoud to a summon. Or, change the interaction as Loreguard wrote, allowing specific attacks to do damage, dismiss or alter the spell effects.
Edit: This was supposed to be a direct reply to Loreguard's post above.