I tend to pick followers who’s strengths are not too high.
At the moment I'm using Brelyna and I carry a few staffs for her to use. I wait until we are near someone who is hard to kill or lots of attacks at the same time, then I give the staffs to her just before we go in.
Every time a follower kills someone or something it's points off me levelling up ~ I don't want my followers doing all the killing ~ I tell them to wait while I go on & clear a good section then go back and get them.
They help me out when I need it but apart from that they are basically a mule there to carry all the loot we pick up 