This is likely Wyvern Sting, been nailed by it a few times in Arena. You can trinket out of the sleep but the DoT... well, haven't seen it get effected by the trinket.
You have to take down the SV hunter fast if you trinket out of it. If not, it's a loss. They can reset and fire that puppy again and you'll be down for the full 10 seconds next time while they chew on the rest of your team.
You need to retaliate with a plan, maybe something like silence, concuss and viper sting (to burn mana on them) then full dps unload. If you got lucky and stunned them, you will likely have them, if not, it's a crapshoot dps match. Your pet should already be chewing on them or their healer the whole time.
SV hunters can be very effective in Arena if played right, as can BM hunters. I've played against both. MM may have a slight utility advantage but ANY well played hunter is dangerous in arena.