[JamOfBoy]

I'm going to preface this by saying the class is Void Assassin, not Void Mage. I don't think we should be giving magic to a class based around stabbing people and teleporting. Black Bolt isn't meant to be spammable. Detogate isn't meant to be Voidgate -> Detogate-d in one turn, it's meant to (hopefully) create space by hitting and teleporting someone too close to a gate, either through your doing or their lack of mobility. Voidgates are meant for spacing, threatening people with your range - teleport, vanishing strike, cutthroat - and for that, they're exceptionally good gap closers. They're not as instantly gratifying as other movement options, and that's fine - sometimes you need that instant payoff, and sometimes you have the time to set up.

In my opinion, you're asking something from the wrong class. VA isn't the source of people getting dark resist, Hexer and DH's Matador are more attributable to this problem - give the resist busting to the classes who use the element more. Something similar to Priest's Divine Judgement, maybe - but that's for another post.