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Yes to Rotom-W revamp.
And I think if we're running that much in terms of Defense, it might just be worth it to make it Bulky Pressure instead of a sub roost revamp.
Yeah to both. Put High Horse Power as a slash with Knock off. I would possibly put Powerwhip as a slash for Horn Leech (guaranteed OHKO on Hippo, Garchomp and Defensive Great Tusk even in sun at +2), or at the very least an OO alongside Trailblaze and Rock Tomb.