Reaper is incredibly satisfying to play. It has the advantage of being designed from the ground up for this expansion, and it all comes together quite nicely especially in the 86-90 range. The core gameplay mechanics are relatively straightforward, but it doesn't feel like you have any downtime, especially with how frequently your burst window comes up in later levels. I'd play it for the gap closer alone, it just has so much versatility. I can definitely see the appeal of playing melee dps.

It's worth noting that the Mark of Death debuff stacks to something over a minute if you really want to, so it's fairly simple to manage.