How does one beat Leeching Life or Fast Shield Regen enemies?

I’m a new POE player, playing as a Level 20 Templar in the Riverlands area with the monkeys. I’ve run into two enemies and they both have insane shield or life regen. I can’t do enough DPS to whittle them down without them netting positive health because of their passive.

Am I doing something wrong? Or is there a specific build/item you need to kill them?

Thanks in advance :)

Edit: Level 20, typed wrong character level at first