Question: Pokemon Black Elite Four?

Answered:
Your levels are ok. Personally I'd have them all at 52 but that's me.

Answered:
Your team is well balanced and should be able to beat the Elite Four. Make sure you are using items to power up moves if you are constantly gettign the opponents HP down to the red bar.

Anyway, I like your team, it exploits most weaknesses in the Elite Four. One change that I would make if I were you would be to exchange Swoobat for Sigilyph. With Psychic, Air Slash, Ice Beam and Flash Cannon, Sigilyph becomes a nice all-rounder that can turn a bad situation into a good one.

For the rest of your team, they seem to be good but I suggest teaching some moves to your Pokemon that are more powerful than your existing moves and also help make the Elite Four a lot easier.

I believe your team should have moves like the following:

Emboar – Flare Blitz, Heat Crash, WIld Charge, Brick Break
Seismitoad – Rain Dance, Surf, Earthquake, Sludge Bomb/Sludge Wave
Swoobat (if you want to keep it) – Psychic, Psyshock, Air Slash, Thunder Wave
Zoroark – Night Slash, Flamethrower/Retaliate, U-turn, Focus Blast
Eelektross – Wild Charge, Thunderbolt (better accuracy than Zap Cannon), Acrobatics, Crunch
Vanillixe – Ice Beam, Hail, Blizzard, Water Pulse

At the moment I would rate your team a 7.5/10 as it is good but can be improved.

I hope I have helped you in some way.