Just to join this interesting discussion: Herald sounds really good to me.
Mystic has a nice ring to it but I dont see all the characters as mystics, Mo&Krill are definetely not arcane.
Ascendants, Aspirants, Acolytes would also fit quite well.
You could of course even more generalise them and...
Shockblast could be interesting as a sort of melee/taser ability with small range and probably a notification for enemies shortly before its cast.
Nanobots is a cool idea in general - there is much wich could be done with that. I would love to give you the idea of a giant blast/laser as ult we...
A mad woodcutter with the usual red/black flannel shirt possessed by an old nordic ghost (viking?).
Main Weapon:
He would throw axes (horizontal and vertical with the mouse buttons for eather wider spread or longer range). Im unsure if they should be stopped by minions or pass through them...