Nothing to do with sims. The devs' testing in T15 showed unholy ahead by a significant margin. So like I said earlier, there must be some heroic bosses with tons of high-health adds and/or important execute phases.
https://twitter.com/Ghostcrawler/sta...91481643192321
Magdalena has a point, though. If unholy and frost are roughly equal performance, most players will use frost for several reasons. First, they've been frost for all of MoP so far. But also cleave, ranged damage, and burst capabilities. Thing is, the proper way to address
that stuff isn't to tune unholy to do more single target damage than frost, it's to
fix those mechanical disparities.
Since that obviously isn't going to happen before 5.2 goes live later today, the devs chose to buff frost. I expect
some players will choose unholy, because it's a more valid choice in 5.2 than it was in 5.0/5.1. But for those of us that enjoy frost there's no reason to consider switching.