VS INDIVIDUAL ENEMIES: Dance around acid/molten pools, spam plague bats, avoid damage further with spirit walk. Cool, underrated thing about bats: goes through waller walls. Alternatively, if a wall (or even better, corner) is there, just spam bears while Gargantuan tanks.
VS GROUPS: Pop spirit walk, wade into the middle of the group, and hit soul harvest and locust swarm before spamming bears. Locusts will gather hordes towards me, and the huge damage of bears and grave injustice will kill everyone pretty quickly.
Using Skorn, limiting AS, and using both Blood Ritual and Spiritual Attunement are necessary to make sure I virtually never run out of mana.
Spamming bears is nothing new, but I like Locust Swarm way more than I thought I would. Ringing the dinner bell. Meanwhile, plague bats has a fun mechanic where it will keep doing damage for a few seconds. So, in small groups, I usually spray bats for a second, then spam bears. Basically damage from two channeling skills at once.