For what it's worth, on T1, I've pulled the initial Cad (didn't think about marking - good call), and hold him on the edge/tip of the three platforms. Then on split, I pull him back against the wall, or at least a little away. This pulls them apart which can make things a little easier. And as OT, pulling away, I start watching his HP closely and when I estimate the split will happen in a few seconds, I combo REALLY slowly, and either have the full RoH last hit ready, or about to. If it's not ready for whatever reason, I hit him once, flash or CoS (which also DoTs the first one if it's ready) and am already running across the room, and finish the RoH combo when we stop. I usually hit CoS when I've already started moving. Unless the DPS start on him, I have yet to lose hate there.

Tip - if your last hit of your hate combo is ready, hit it, and during animation, you can start moving. The hit will finish while you're on the move. You don't have to stand and wait for it to finish.