Call me a killjoy if you see that fit, but ”Greyview explains to Oona with facial expressions and gestures and without much difficulty that Team Evil should follow him; Redcloak realizes immediately that the clerics are somewhere behind them; he lags behind as Oona and Greyview begin to move back towards the door until he's out of range; he dispels the silence spell; and off they go” sounds a lot more likely than ”Team Evil almost dies and then X. kills Greyview.”
Also, I don't expect that we are going to see how Greyview delivers the message.
While I find the idea that Minrah is soon to die less than feasible, I would presume that those who believe Minrah will die base that assumption on the fact thet she is not a core member of the Order, and (according to the Giant) not a member of the main cast, either. As such, she is indeed a more likely candidate for getting killed were Team Evil to demonstrate that they are still a deadly threat than any member of the Order (including Belkar). Needless to say, since we know well enough what Team Evil and its individual members are capable of, such a demonstration would be largely gratuitous.