Harvesters are really easy when you figure out what makes them tick.
What you need is a point-blank AOE damage skill (steel tornado from dual wield line is perfect)
1, get close to the harvester, and keep circling around it while hitting it. This will cause his cone spell to miss you (he will cast it at a spot you were at 1 second ago)
2, when he lifts you in the air and summons 4 balls that float towards him and heal him, break the stun and spam AOE. This will kill the balls and heal you instead.
Well, before 1.1.2 we could actually BASH (and so stun) her while she's casting Black Winter, instead of being forced to run around in circles like crazy. Also, if harvester is near the wall, even CCbreak won't be quick enough - an orb will spawn almost directly at her and immediately heal her.