It's not a bad idea, but how about an extra die every 2 shots or something? 1 per seems a little excessive to me.

Well, it's 1 die per shot, and +1 (or even +2) TN per shot, so it does more-or-less even out. It makes dodging somewhat harder (since there's a chance of more attack successes), but resisting somewhat easier (since the attack's Power isn't increased, and the damage is only staged up by successes).

... and then it'd still be nigh impossible to hit with even 1 shot from the vindicator.