I guess we are doing something wrong on this boss. (Not a heroic raider here, so this is the first time doing this boss on Heroic.)
We were working on him last night and I noticed that when we were downing the protoform barrier orb (?) it was immediately transitioning him down below 70% health. From like above 90% I think?
So we’d do the run to the middle mechanic and then all fall to our deaths as the falling damage seemed to be large.
I am guessing we are not handling burden of sin, the barrier and all the soul adds correctly somehow?
Any ideas/help would be welcome on this one.
You need to have 2 or less stacks of Burden of Sin to be able to safely reach the center during March of the Penitent (70%), unless you have access to any ability which prevents you from being slowed beyond a certain threshold. If it requires an activation, like Ghost Wolf, it needs to be activated before Denny hits 70% and starts the March.
As for buying enough time to shed the initial 5 stacks from Heroic, a raid group will have to adjust their DPS until everyone has dropped enough Sin stacks.
One method is to have the entire raid soak the 2nd and 3rd Cleansing Pains after one half eating the first to offset Blood Price. This would allow everyone to reach 2 stacks by the second Command: Ravage of Phase 1.
Yeah we were trying to play around with the sin stacks.
I think the Protoform Barrier was causing trouble. I didn’t realize that when the orb dies it channels all of the damage taken by the raid directly into the boss. Which was causing boss health to drop below 70% before we were ready.
We were thinking maybe you leave the orb up? I don’t think it protects the soul adds, so you can still dps them? We were only seeing 1 ravage before boss health dropped below 70%. The drop was insane. Like from 92% to 70% instantly? Not sure. It was unexpected how quickly it went.
A couple of pulls we tried having the entire raid eat the Cleansing Pains to drop stacks. Damage was too great. We didn’t try a split soak first and then an all raid soak on 2 and 3 tho.
I need to do more research. 
Thanks for the response. I appreciate you taking the time to read and respond.
One of the hardest things to do as a raid leader is to convince the raid to stop doing damage. If Denathrius is getting pushed too fast for P1, then players will have to sit on their thumbs until enough Sin stacks are removed to survive into P2.
Progression didn’t quite have this problem as current reclears, but players just need to use the big head and save their damage for P2 and P3.
P1 you must throttle your DPS and be prepared to hard stop DPS in order to make sure everyone has 2 or fewer stacks of the debuff. If you can time your roars correctly you can get away with 3.
The cone is tiny, you need to stack tight. Stack means stack, not stand next to. You should see 1 giant blob of character models where your tank is if you’re doing it correctly.
This is one of those fights where you need to be prepared to sit people who can’t do the mechanics, especially if you lean more to the casual side.