TL;DR at bottom of post. [SHAMAN ONLY]
Edit: Totems/pets are not supposed to stay out when you mount a vehicle.
Greetings.
Today I was doing the daily "Back to the Pit" for the Polar Bear mount.
I accidentally dropped my full set of totems (including Magma Totem) just before hopping on the bear.
I noticed the opponents dying rather quickly and noticed Magma Totem was damaging them.
Quest was done in about half the time it usually takes for me to do it.
Not major, but should help a bit I guess.
TL;DR:
1) Get daily quest "Back to the Pit" on your Shaman.
2) Drop Magma Totem before getting on the vehicle. (Drop it near a bunch of opponents)
3) Magma Totem will also damage them as you kill them.