I think they use the normal bip skills, and then symbiosis and edge of exctinction. Not positive about that though. I actually don't believe those 2 skills are required. They really don't help all that much.
One of them for example allows someone near the spirit to gain +2 health regen. But the only people that will benefit from that are casters, and they wont be receiving damage anyway if the group knows how to handle aggro properly. It's literally just a waste of energy.
I've found that most teams want you keeping up bpi constantly on multiple people. So you need to focus on that. And considering many people run low health builds, you also need to protect yourself so I always play n/mo and bring some healing skills like heal area, and also bring prot spirit just to be safe.
EoE Symb and maybe Qz. Remember to keep up Symb all the time if u have balanced team coz in trapper teams u dont have to bring spirits rangers have much better spirits so u just have focus on bipping
im usually 1hp or 55hp depends where im going....if im going to foundry i think 55hp is better there but u get urself killed so many times cause of those gates and ppl have to rebirth u to other side so u usually have alot dp...sure u can bip while u r 1hp just find a good spot where u can bip all and remember to bring another armour set...in veil and gloom im always 1hp som1 just have to bring me res chant coz while im 1hp i can spam bip all the time coz i take 0 dmg so it makes my job a lot easier