Hello Strongmen of Sactuary,
i tried the last two season to get a Rend Bleed barb going. With Shattered Vow, because in some weird way, i have a sweet spot for this item.
Got to T3 and then it was over. Asked for help here, got some (thx again), but what i got, was in the end, that rend is not very effectiv for bleed.
New try now, but this time, i ask before i start. I want to find to try my own version, netherless, my question.
Is Rend an viable option (for T4) together with all the damage over time boss powers?
Yes or no would be enough fopr me as answer.
Thx for answers in advance. 
Rend continues to be weak. Rupture with Third Blade can be decent in T4 but Blizzard has a long way to go with DoTs. The damage potential should be much higher than Direct Damage.
Shattered Vow continues to be a problem because it takes up a coveted 2H slot. The Aspect on it needs to also have a damage modifier and not just be an Execute when Bleed exceeds enemy HP, which is stupid. This just saves you a Rupture.
I digress though, the most fun Bleed build that I have found in S8 however is a Brawling build to focus on Ground Stomp (and Power Kick) to apply Bleeds (Ravenous) and not having Rend on my Skill bar at all but fully maxed out. You can double dip with Berserk Ripping on your Brawling DD damage and the Rend Bleed is respectful. Stuns are so prevalent with Boss Powers and Ground Stomp you can watch chunky damage from Skullbreaker proccing all the time.
This isn’t a build you will see on Maxroll but that does surprisingly well. The downside is that you have to have a 2nd set and loadout for Bosses to shift away from Stuns and focus on Overpower Power Kick Bleed. With a Banished Lords, you can have every Power Kick Overpower. This allows Gushing Wounds to proc every Power Kick but you can also make Unbridled, WA, and Unconstrained all work.
Tried Rend/Rupture with Fields of Crimson. T4 was doable but a struggle and couldn’t do lair bosses.
Hit pit 65 easily then switched to double swing.
Picked up a shattered vow and am going to try a pure rend build sometime in the season.
Will let you know how it works once I try it!