An interesting concept.
A few things concern me about the mechanics. Tukulis ilustrated my thoughts about how swapping position could lead to some very overpowering (unsurvivable) circumstances. In a game that usually ends up being mostly about positioning and knowing when to push (or pull out), the ability to control an opponents footing seems pretty powerful. Even if they know when to retreat or back off, a simple key press puts them back behind enemy lines. Its basically a gank on a timer for any teamate assigned to capping flags or a solitary lane camper. I know it would be cool, and definitley fun to use. I suggest (at the least) to make the swap count toward the same timer as stuns, so that he can't be lured backward into a waiting stun. The idea is too fun not to want to play with, so I can't condemn it.
The passive crit ability. There won't be much room for any sort of buggy implementation there. It could be game breaking if it releases with odd buggs that cause the crit to effect all skills/attacks, or not align with other crit buffs properly, etc. On that note, how much or a crit/overall damage are we talking about here? As well as its expected proc rate? I don't think there is any ability in the game that has a crit chance at all so far, so this could be pretty interesting. But it also sounds like it could be too powerful, unless respectable damage is dependent entirely on whether or not it crits, and its otherwise negligible. That would add a lot of tug rope play to the character, if its assault more or less depended on whether its opening strike was a crit, which could be pretty fun. Still I can immagine how annoying a crit fireball, snipe, etc would be. Adding a chance factor into skill usage is interesting, but could lead to some balance issues down the road. Especially since demigods that focus on auto attacks already stack good ammounts of crit. Is this going to be a Demigod that is capable of teleing on an opponent and staying on him with auto attacks until hes dead? Like an Erebus/UB hybrid, perhaps. That sounds pretty potent. If hes going to be as able to do that as beast, with better tele in/out (opener/survivability) than previously available in game, I think it would be too powerful. I have some ideas on how to remedy power imba, if its even there. Pointless to go into it here where its theory based on a demigod proposal.
Are you going to release some sort of test version, or just straight up release it in a patch? I'd definitley be in line to help out with any issues that may be there. I do like, at first glance, how you left off snares/interrupts/stuns. Even as just a concept, those added abilities would be way too powerful (as he is) which is no doubt why they arnt there. So props for an eye to good balance, to whoever was responsible for the idea internally.
On an aesthetic note.... It does look insanely Giger-esque. Whether intentional or not. I'd have to wait to see better concept images or 3d rendering, but in your concept art I think the sword and dagger look very.....well un-appealing. If hes going to look like some boss demon with a beastial carapace and lots of sharp points on stacked plates of armor, it would seem to be better fitted with claws or perhaps katar type weapons (maybe even actually attatched to his armor/carapace as a built in weapon, but still independent from his hands). Alternatively, he could be more humanized to look better with weapons. Just a thought. And totally just my oppinion, unrelated to the above .
Can't wait to play him and see for myself..
EDIT: P.S. A demigod with passive evasion. I was really hoping one of the new ones would have this. I can't wait to try out the itemization combos I've envisioned with this ability.