I think Jolteon had more of a niche in the Tornadus-T metagame. Although it couldn't really switch in, Jolteon could at least outspeed Torn-T without the need for a Choice Scarf unlike Thundurus-T, so it was free to run a number of sets without needing to be locked into a move. In the current metagame, I'd say Jolteon's viability has dropped a little - its speed tier isn't so useful now that Tornadus-T is gone, and it's still much less powerful than Thundurus-T in general. I think C-rank is probably the best place for it, though it is one of the better C-rank Pokémon out there. It does have at least two sets worth using - the SubPass set and the EBelt. Although Thundurus-T's EBelt set (Thunder/HP Ice/Superpower/U-turn) is much better at simply breaking down things, Jolteon's EBelt set (Thunder/HP Ice/Signal Beam/Volt Switch) is much more effective against offensive teams because its speed tier gives it the jump over almost everything that doesn't hold a Choice Scarf. I don't really like Choice Specs since it isn't strong enough to get away with mindlessly spamming attacks, and Life Orb cuts its already short life even shorter.