That Cobalion loss reminds me a lot about how I lost my Durant+Shuckle streak, except I was beaten by that stupid Brightpowder Gothitelle... Do you just run max Speed on Gothitelle? When you mentioned Gothitelle I sort of wondered whether there was some sort of "ideal" Speed tier to hit although I didn't really come up with an answer. If you were pedantic about it you could knock a few EVs off of Speed since you only need 244 to outspeed everything you possibly can with a Scarf. (You just miss Weavile at max but Bisharp can usually handle it, assuming it doesn't get frozen). 212 would give you enough Speed for Base 115 Speed Pokemon (and a few more can beat Zebstrika) so maybe that's a good way to go? All of that assumes a 31 Speed IV of course. I'm probably overthinking this!