I don't have a MB, so can't comment on its effectiveness. However, if it is anywhere near as useful as having SI on an entire raid at all times, so long as the LMs are mindful, then... Damn straight I'd use a MB in RvRs to counter. Until then, the only thing to do is adapt and find a way around the enemy's strengths. Or, do as what many other people do these days: Pay to Win with store brands!
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