Flash Fire Skarmory is probably the most used Skarmory around, due to fire spam. Plus, that's STILL a 2HKO, which allows Skarmory to whirlwind it out.
What motherlove said. I didn't want to expand it too much, since that would remove players ability to customize their team to their liking.
I never said the Sylvedon core would be flawless, but it doesn't have many common counters. (Venusaur and Empoleon are nearly non-existant in this meta. I haven't seen a single on of either of those in all the nearly 150 battles I've played.)
With how frail and fast Regenerator Jolteon is, it really doesn't make a good Regen Switcher due to it pretty much dying if something even looks at it. Rotom-W would make that set a million times more viable, though, with access to great pivot options in tricking a specs/scarf, will o wisp, and a nice slow volt switch to safely bring in team members. If you are going to continue using Jolteon, though, Life Orb would be better than Choice Specs due to you being able to access a lot more coverage/volt switch, and being able to simply negate it's self destructive effects by switching out.
I'm fairly sure that's a problem for almost every non-unaware mon not named Keldeo.
EDIT: Ignore my brain fart about the unaware pokemon