I started arena again after I took a long break and drafted paladin. First run and I had a 6-3.
http://www.heartharena.com/arena-run/0ju873

Some of the cards I felt that are OP or overpowered:

1. Murloc Knight - esp. power up and get another Murloc Knight + a Silverhand Recruit
2. Seal of Champion - basically a free kill at the early stages
3. Mukla's Champion - if you have board or Muster for Battle before hand
4. Kvaldir Raider - somewhat effective since it's only a single threat

If you see them in arena drafts, my recommendation is to pick them.

Update: It is way scarier when fencing coach turn 3, then play it turn 4 with a free hero power. But then you've basically skipped turn 3 by only playing a 2/2... so there is a trade off. - credits to FuryBull