Upon zoning into the Arena instance, players start in a "holding area", health, mana, and energy are all restored, all buffs, conjured items are removed and pets are dismissed. (Debuffs will remain, and pets can be resummoned once you zone in.) Players are also given the Arena Preparation buff, which removes the casting cost of all abilities (including Soul Shards).
Current situation: Buffs don't fade from hunter Pet. http://www.pic-upload.de/view-20921259/WoWScrnShot_100513_135026.jpg.html
Desired situation: All buffs should fade at zoning into the Arena instance,
wowwiki: