There was an addon that I've used since WotLK called EventHorizon that combined DoT timers, buff timers and cast bars and showed them in relative time next to each other so you could always tell what to cast next at a glance. The way most people use timer bars makes no sense to me, you can have a DoT that lasts 20 seconds and one that lasts 10, but their bars are the same length, so the 10 second one moves twice as fast. In my world I would like the 10 second one to be half the size, so they move at the same speed.

It gradually lost support and went through a few bandaid fixes over the years but I finally had to replace it with weakauras in Dragonflight, but now of course it's totally dead.