You can handle this one of two ways. My suggestion is always do the other bosses first. If you wipe on one of them, well then the group sucks anyway and would never have downed the latest boss anyway. If you dont do them first because of bitching make it clear that you're going to be doing at least 2 of the other bosses and keep track of who leaves. This works suprisingingly well. Last week we did a pug ICC25, we get inside, cleared the trash and then I checked my list. We booted one guy who left in the previous VOA. He bitched and moaned about why he was booted and we said we really need people who dont quit on instances after getting what they want. Works like a charm. Didnt have any bitchers this week in VOA.