Tell the whiners that if they want to raid lead, the door is that way. Also, link their fails back to them in tells (not raid chat).
People like that are poison and if they won't stop after you've made your position clear I'd strongly consider kicking them after a final warning.
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Not relevant to the OP though. If you're wiping to DPS issues then sure, sitting the bottom DPS, especially if they're far below the average, can help. So can sitting the people who always die to avoidable damage. However, if OP is being accurate, the complainers are as guilty as others of mistakes.
Also, a couple of wipes just aren't a big deal and people who whine over them need to get a grip.