I would absolutly love this idea. My RoBF wearer is my evasion minion, and I have a PL wall aside from him.
So personally I would get a huge buff.
How is that a buff? Did you not have kill slots in front before (I am assuming your NCB plan)?
If you had kill slots in front before, then the Msk just bypasses them, targeting your robf minion, thus a 'nerf' (speaking in terms of nerf->buff). If you were planning to put your evasion minion in front, then it would have gotten hit by tanks first anyway, so the Msk (specializing in targeting it) would also be a nerf (because you could put a base DD spell on something else and have the msk target that first, thus creating a killslot), or if you were only two minions, thus benefiting from the evasion (other minion is a PL wall?) and not having room for a kill slot, then there is no change to your strategy, and the Msk BUFF (because it is a buff) wouldnt affect you.
Sorry if this is trollish, but this just struck me as peculiar.