Is it possible to demand to give things a second chance? in this case I demand that M-Mawile get a second chance as the set on the analyses, although thought to be good by people like Melee, the set choice was terrible. The 2 sets should be SD/knockoff or sub/suckerpunch/play rough and sdef or even just another spread option on SD. I don't know why you're even considering iron head when play rough (fiary aura) + sucker punch straight 2hkos every relevant geoxern spread. Rock Slide is very much so inferior to Knock Off:
252+ Atk Huge Power Mega Mawile Knock Off (97.5 BP) vs. 248 HP / 0 Def Ho-Oh: 218-257 (52.5 - 61.9%) -- 98.8% chance to 2HKO after Leftovers recovery
252+ Atk Huge Power Mega Mawile Sucker Punch vs. 248 HP / 0 Def Ho-Oh: 180-212 (43.3 - 51%) -- guaranteed 3HKO after Leftovers recovery
and pretty much everything coverage wise is worse than +2 SP or knock off (if you don't choose sub because that's important vs non steel arc even then:
+2 252+ Atk Huge Power Mega Mawile Play Rough vs. 252 HP / 0 Def Arceus-Steel: 237-279 (53.3 - 62.8%) -- guaranteed 2HKO)
here's my team if you want to try: CB ho-oh/knock off SD mawile/rest palk/impish lando-t/shaymin-s(healing wish)