The problem is that you give up something better to put Rend on the bar. Its damage is negligible and PE takes care of its own bleeds. So does having the BK Wedding Band on your follower. Between PE and the BK Band, you have all the bleeds you need in density. There’s zero need for Rend and it contributes nothing of worth to the build.
In its current state and in every possible configuration, the build with Rend on the bar will be weaker than the build without Rend on the bar.
What tier? It takes more than a screen. We’re talking about optimal density for the build, so you need Festering or Battlefield with 3+ screens all grouped together. If you can submit video, that would help, because if what you’re describing is accurate, there has been some kind of server update.
No. Spenders shouldn’t be cast without their animation, and anyway, that wouldn’t fix the problem with Rend’s negligible damage. Adding Rend to the Wastes 6 bonus is only step 1 of getting it to deal worthwhile damage.
The point of the build was never to endlessly whirl. It was always, from its inception, to gather density, Rend them, and then whirl. Even the Blizzcon preview of the set had that baked into its design.