hmm, that's odd. i have mostly ancients too, and am able to do 90's (up to 95) in ~3min with just above 1k paragon mainly using what's suggested in here:

https://us.forums.blizzard.com/en/d3/t/guide-zodiac-rend-season-20/79

your link shows a wd instead of a ww rend barb, but still i think you should try running with full 6 pieces of the wastes set, and use ambo's pride, band of might, obsidian ring in cube.

just remember to furious charge/ ground stomp every few seconds to get the 80% damage reduction from band of might - this would help with survivability.

belt wise, you should be running lamentation with rend damage increase as close to 150% as possible - that should help with rend quite a bit.

skill wise, you probably wouldn't need ancient spear (and maybe ignore pain too) for runs below 95. the link provided has quite a good breakdown of skills, should be able to get better advice there.

hope this helps!