If two mobs come at the same time: in fact your pet could tank both of them, but its HP may lose quickly and you should always stop shooting to healing your pet. Simultaneously, the mob which has been attacked will keep on attacking your pet, while the other one might OT. When you are healing your pet. At this time, you should set a freezing trap when that mob heads to you. Or you could set a freezing trap once the battle starts, using Distracting Shot to pull that mob,(the one that your pet does not attack), and it will be entrapped. Please remember to put another freezing trap when the previous one is about to lose its effect. Kill the other one together with your pet and then kill this entrapped one.
If there are more, eg: three mobs, then it will be a little difficult. First you have to use freezing trap to entrap one, let your pet to attack one, and for the other, it might OT and turns to you when you are healing your pet. You should use Feign Death at once and it will go back to your pet, if OT again, you can use your pet to taunt it back. During his running between you and your pet, you should try to use those three skills: The Beast Within, Rapid Fire and your trinkets to kill the first mob your pet tanked. And then your pet could tank the other which has not been trapped, and then the last one. In short, you should kill the mob one by one. It's easy for a hunter to kill the outdoor mobs (not elite one). While there is one more thing to pay attention to: ranged attack mob and mobs using spell attack should be your first killing choice. You can use Scare Beast to stun this kind of mob which will cut down their spells and always they are easy to kill. When the first is killed, things will become easier now.
For simple team quest with only a elite mob, hunter could complete it by himself. Just as you are killing a single mob
First mark it,
then misdirect your pet and shoot the mob, pulling it to your preferred safety battle ground
use serpent sting
And steady shot,
Healing the pet when it starts to lose HP
Use Feign Death or misdirect your pet when you are about to OT.
Remember to use Scare Beast as earlier as you can and keep on using it once it is ready from cooldown.
After a while, use the Beast Within and any trinket you have, as well as Rapid Fire.
If your pet is losing HP faster than you can heal, it might be killed. Now you should use Distracting Shot to pull the mob to you and use Hit and Run strategy to win some time for your pet's regeneration of its HP. When you think your pet is ready, use Feign Death and your pet will get Aggro again from the elite mob.
If your mana is not enough, please use Aspect of Viper.
You can use Kill Shot when the mob has only 20% HP left.
Keep the dot of serpent sting as well as steady shot until the mob is killed.
Generally speaking, a hunter could complete a team quest alone where there is only one elite mob and for which requiring two or three players usually. Of course, you need to be well prepared with a clear mind and skilled operation is necessary.