What’s confusing?
Vampiric Touch = 1 button
Dark Void = 1 button
1 + 1 = 2 - That’s 2 buttons to do the same thing 1 button can do.
Shadow Crash = 1 button
Savvy?
Now address the rest of the issues with your idea around PvP and counterplay. You can counterplay the current iteration of Crash and my mob targeted version of Crash.
If you don’t see how your idea can cause issues and QQ from people then I don’t know what to say.