Since the Mindcrafter's greater mental blast uses what I assume is the targeting feature developed for missiles, the visuals get blocked by walls but the skill definitely still hits and does damage even without the green X being on creature. And as such it's is hard to tell/know that the [i]nvoke doesn't get blocked/mitigated and the damage goes through anyway. If it was a floating green "X", without the connection back to the character @, it might work better.

This in the noteye ASCII version of 3.0.6