Even though I have mentioned this issue in some other posts concerning Grim Focus, I wanted to make a different discussion for it.
So, with the new changes to the Grim Focus ability, the stacks you have built will now remain when you recast the ability or if the ability runs out. Exiting combat combat though removes all stacks. In Maelstrom Arena, every time white portals spawns and there are no others adds alive during that point you are technically out of combat, and thus all stacks are being removed. So let's say you have a spectral bow ready. When you finish fighting a wave of mobs and the next ones are about to spawn, you are gonna lose your bow proc, because during those 3-4 seconds when white portals spawn, you are out of combat. For the average player, this might not be that much of an issue, but for players who are pushing for the highest of scores it is extremely discouraging, as it decreases your overall performance in vMA. I would like to see this addressed as soon as possible. Here are the videos, including both morphs of Grim Focus:
Merciless Resolve: https://youtube.com/watch?v=elEBGR9d4KoRelentless Focus: https://youtube.com/watch?v=w-2SPZ6C34Q
Maelstrom Arena - World's First Nightblade 600k Score - 02/18/2017