You're not wrong, but Otou already said this 2 posts above you.
Another benefit for RC ( not saying it makes it optimal by any means) is RE can only proc if you have a rune on full CD so avoidance streaks etc where you are sitting on a deathstrike you can fill GCD's with rune strike and speed up a second DS for when you do get hit. With RE one has to sit on your RS until after the first DS ( second set regening) and then hammer away to try and get a second deathstrike in the large absorb window.
Again not making it optimal but one small thing in its favor. ( Obviously blood tap does this better since you can bank your DS's but requires you to bank it/ ramp up time.)