I just tried it today in a raid, after my Doom Tracker based on Weakauras failed after the update.
It is plain, simple and easy to spot.
I haven't found any settings or options to configure it... Just hit the training dummy a couple of times and when it came up, I could place it where I wanted on my ui.
It makes a small sound once mark of doom is triggered, so you wouldn't miss it. The small window even tells you which mob it got triggered on.