Sylveon: Replace metronome with choice specs, since you get a 1.5 times boost immediately. Sylveon's physical attack is very weak, so hidden power will usually do better than the coverage moves you gave it. Psyshock is a much better alternative to hitting poison types, and it lets you hit special walls slightly harder. Hidden power is a good idea, though whether you want ground or fire depends on specific threats. Shadow ball is just good as an alternative coverage move.
Serperior: Leaf storm is already powerful enough, so frenzy plant is slightly unnecessary. Besides, if you're going for a sweep, frenzy plant will cripple you. Replace it with hidden power. Whether you use fire or rock depends on specific threats. If you choose rock type hidden power, the occa berry will be unnecessary, and life orb would be better. Hyper beam will do the same as frenzy plant, so replace it with dragon pulse.
Shuckle: Replace power swap with infestation. Opponents can switch unlimited times in a battle, so they can easily wear out your PP that way. Also, switching out resets the counter on toxic, so it won't do as much damage.
