I don't see why you want to single-target adds during aoe phases. It is dps loss and not required for killing Iskar.
You can toss the eye and deal with chains (on mythic) and other mechanics. You don't really need any specific add to die fast.
Why just don't kill them all instead?
But if you want to tunnel a specific add as BM you can do it as well, just check top Iskar parses for damage to specific targets. It's actually even easier for BM to save burst cds (MM's Rapid Fire has 2min cooldown and will not be up for every set).