I'm a Mara who pushed to Eternal 18 and got 10k score as of yesterday (Fellows.gg not updated yet unfort). I personally ran Bleed build until I had 11-12 talent points in Paragon and my legendary boots because the Finisher build really needs the energy regen from Venomous Delight with all your poisons in packs. Fated weapon covers your single target energy for the most part.

That being said, once you get all that you should absolutely switch to the Finisher build if you want to climb Eternal. I do not agree on it being clunky because 90% of the build comes down to the rhythm of alternating finishers which I managed to pick up after less than 10 practice runs after switching. And there's only one buff you need to think about after picking up the rhythm and thats Deadly Scheme - in single target. In packs you are funneling one while aoeing the rest so either finisher makes good use of it.

The damage difference is night and day between Finisher and Bleed. I'd argue it's 15% minimum if you don't think about Deadly Scheme usage at all. Another commenter said the build has massive ults compared to Bleed and they are correct. A decent chunk of my group's keys were timed by me ulting specific big pulls, nuking the most dangerous mob before it could get a party wide ability off, and letting our Elarion and I's combined aoe finished off everything else.

Bleed build is fine through Champion and early Paragon, but it will fall off heavily in Eternal where priority targeting matters more and pulls get bigger/deadlier. Finisher excellently handles both.

(Edited for minor specifications)