Deadeye Mirage Archer cannot use Plasma Blast crossbow skill

Putting Plasma Blast on your Mirage Archer causes said MA to appear, but they just stand there, menacingly. Probably related to the fact that it needs to be channeled, but there is nothing stating in-game that MAs are forbidden from that, so I'm assuming it is a bug.

Give my greenie his slow ahh laser pls