ok, a lot of playing, imho, breaks down to:
talent/builds
strategy
gear
and pet is like it's own separate.
for a great site about pets, go to petopia http://petopia.brashendeavors.net
cats have the most abilities, including prowl - which we have talked about. With eyes of the beast, it is invaluable.
boars have a charge/intercept/stun ability, which lots of hunters swear by.
wrp chasers have their warp ability
turtles have shell shield
wolves have a howl that adds to all physical attaks of allies
the big birds have swoop, which is a knockdown
(other pet, like gorrila and serpent/scorpid, have ability, too)
for arena, i think cat is still best. For most other BG, hmmm, harder to choose. But really something with dash.
as for scorpid, health is medium, armor high, and poison is good BUT poison can break some kinds of CC, like polymorph, hibernate, your own ice trap . . .
My hunter was specced BM; the key is that you have the best gear avail, since the patch change tied pet stats to you stats.
Take a careful look at the talent build I posted, and we can help get your gear/build sorted