I never post on this site but this topic certainly has my attention...
I never was a fan of Jolteon in the original games because IMO, it really sucked. It didn't learn any good moves until higher levels were reached, and we all know that accuracy sucked. It is on my Reborn team now, but that's because it has a way better move set now. Too many people used to rave about Jolteon that I did my best to never have one until Gen 6.
Oh, and as far as electric rodents go, I had Pachirisu on my Reborn team up until level 50 where I then replaced it with Jolteon (because it was getting too weak for battling that far into the game). That thing got me through most of the game. I always thought it sucked as a Pokemon, but I was pleasantly surprised by how far I got with it. It impressed me.
I also lump Ninetales in with Jolteon because I used to love the design, but hate the moves it learned (well, didn't learn.). It has improved, but it's still not a favorite of mine. I blame it's terrible stats to my horrible luck of getting bad natures and the like, but IMO, it still has room for improvement in that department.
New fairy types would have been nice instead of slapping Pokemon like Marill with it. I cannot stand Marill anymore.