The three rings in the WW/Rend build are CoE (equipped), BoM (equipped) and ORotZ (cubed)…
In the season where we had a 4th Cube slot, we could Cube both the ORotZ and BoM, and wear Focus + Restraint, because maintaining the F+R bonuses was better than CoE. That’s no longer available, so you need the three core rings, because if you Cube ORotZ and wear F+R you’re missing out on the massive protection from BoM.
It’s because you have echoing fury equipped. For very fast speeds that will be better. It’s is the same for t16 key runs. It is better to not even run an ethereal. Just stick with bul kathos blades. This is the issue with ww using ethereals. We need to give up something important in order to use them. Dropping istvans or bulkathos weapon are a big deal to the build.
Godfather + echo fury is good for speeds. The EF effect will trigger your zodiac faster for fast cooldowns and give you actual movement speed. Ngeo is great too. Anything under gr100 bk swords are easier to deal with.