Hey.
After checking the results and hearing opinions I think it's best to give evasion. Because if full invulnerable, the enemies will simply run away doing nothing. If evasion is 100% the enemies will fight and attack Fradz, but won't deal any damage except spells.
This also makes the spell a little more tactical.
You have a point, i've voted for invulnerability, but now that i think about it:
1. Fradz is moving REALLY fast so avoiding the enemies would be a piece of cake, in another words, it would be good since it keeps the coherence.
2.Like Aero said above. It would be very good(even a little OP) since Fradz could take all the hits without taking damage. Skills could kill it though, but i don't think that's wrong...