It seems too strong to me without it. I guess it may be better if it's just a blind not full blindness (Nightvision + Blind) I was just worried because: I'm gonna be able to work wonders with this move, if it comes out. Full blindness or nay.
I just thought about how this just might balance out for an ability like this:
The chi-blocker holds sneak to activate the ability. There would be no blindness which would inhibit its potential effectiveness and the slowness is taken care of because of the sneaking speed. The ability will last as long as the duration for it is set. If the chi-blocker strikes a target the ability will stop.
In this way Shroud could be used for actually allowing the chi-blocker to efficiently position themselves where they want be relative to the target since they will always be able to see them. This could be used both overtly and covertly depending on your actions.
I think invisibility is overpowered for a chi-blocker unless it's rather short duration, but in the case of an ability slowing the chi-blocker down (such as this) a moderate (but not lengthy) default duration would be appropriate. A semi-lengthy default cooldown would also seem appropriate.
This is how I see it working, anyway. Let me know what you think.