Otherwise you'd almost certainly see problems

Otherwise you'd almost certainly see problems with rogues constantly using all their escape/reset tricks just to stall out to the timer anyway, presuming this worked out to be a legitimate strategy in the first place. Two minute Vanish, five minute Prep, and good odds on having enough CC to just drop combat and stealth normally sometimes, too.
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But, again, you also really, really do not want this to impact legitimate uses of stealth, or it becomes a balance change, rather than a cheesing fix.