Solo and group advice for a new shaman?

[Morti]

I just started playing P99 and rolled a barbarian shaman (currently lvl 14).

After reading a couple of posts, guides and watching some videos, I'm still unsure if I am going about this the right way.

Question: What is the most efficient way to solo and how do I best support a group at my level?

Solo: Do you root/rot or do you facetank(?) with slow?

Group: buff the group with dex/agi, slow the mobs and heal in between fights?

Also, I see people advocating for drowsy/inner fire (until you get heal) as they are more mana efficient?

P.S. Yes, I know the join date says "Jun 2015", but I dropped the game back then only to return now =)