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I run Calm Mind, which I'm not sure actually helps or not, considering its primary use is as a countering utility. The boost does help quite a bit late game, though. I don't bother with Speed EV's because I feel it doesn't really outspeed anything worth outspeeding anyways, and Uxie doesn't get...
From experience, U-Turn still does minimal damage anyways, and I can use that to my advantage to either Calm Mind or predict the next switch-in. Admittedly it fares badly against Tyranitar, but that's what the rest of the team is for.
I can attest to that thing's utility in OU, even if I had to use a different EV spread than what the site gave. Gliscor, Hippowdon, and Mamoswine become almost non-issues with Mesprit around, and so does DD Gyarados (barring flinchax). Swampert is practically forced to Roar or flee as it can't...
Mesprit actually gained 0.11% and 19 positions since November. And yes, it's a greatly underrated Pokemon especially considering Porygon2 gets so much attention. Most Ground-types can't do squat to it, it can threaten the otherwise annoying Machamp and Breloom, and it can send Gyarados and with...