I tested it in many ways and marked for death seems to not work right now. It doesn't proc the explosion at 150% damage unless you 1 shot your target. If you don't 1 shot them the explosion damage stays at base 75% as if you have no mods on. Overextended with power donation and it still did 75% in a aoe blind rage and still 75% in a aoe. And It isn't scaling with health either. I've 1 shot heavy gunners with enemy's that should have small health pools in comparison. I tested in the simulacrum, on MOT and on steel path MOT. Marked for death is broken it seems.