I think most of you already know it but I hope that I can help at least those that don’t.
The easiest was to beat a hunter / lock (with Felguard) is to cast Mark of Blood on their pet. A decent DK with 25k health will be healed for 1k health per pet hit.
Most of your opponents will not realize that their pet has the debuff and will send pet. Some experienced though will kite you until the debuff wears off.
EDIT: It's was posted here by mistake. Please move it to Guides