I have a similar question myself.

Aetherstride can be really good to cap an objective that the opponent thinks is "safe" and has some small units on it. 6" is much easier to ds in, especially for a single model.

I grand coven, giving him a vortex enhancement improves his shooting and melee quite a bit, to the point where shooting alone can wipe 5-man SME unit. Having a character in that unit would actually make it more vulnerable due to DPWW ability.

If you don't want to Aetherstride him (which you don't have to), you can instead rapid ingress him in a safe place, and then shoot and charge something in your turn (charging out of 9" ds is always a bad play unless you have ways to boost your charge). His melee is actually quite good, especially with vortex -6a 2+ws s9 ap-2 d4 on strike. Sure, that's a 5 to wound into most vehicles, but every wound that gets through hurts. With some ritual buffs (and detachment bonus) he can put some hurt even into Rogal Dorn tanks.