TLDR: Branns damage is more than halved in all delves and also for the Underpin for Druid Tanks (~0.7M DPS) and maybe other Classes/Speccs in comparison to Prot Warris/Blood DKs/Brewmaster Monks (~1.5M DPS). Also Brann scales with crit/versa and maybe not haste/mastery of the character instead of a pure ilvl based scaling (which in my opining should be).
I found the following on reddit and had the same issues. I hope some of the dev team will see it here and look into it:
"I want to add this here as a tip for all delvers and also as a potential note to the devs. Recently I noticed that all kinds of delves feel easier on the Monk Tank than on the Druid Tank. As an info on my Monk Tank, I defeated the Underpin on ?? some time ago and wanted to do the same on the Druid Tank. I realized that the fight is significantly harder than on the Monk Tank. So I just checked the logs and this is what I got:
Brann (same for both): Max level, Magnetic Grenade, Bioprinter
Druid Tank (ilvl 664) and Monk Tank (ilvl 660)
The results are surprising in terms of balancing. During test fights against the Underpin on ??, Brann’s DPS looked like this:
Brann DPS on the Monk Tank: 1512k
Brann DPS on the Druid tank: 735k
The example of the magnetic grenade shows it particularly well:
Average damage per hit on the Monk Tank: 10.56m
Average damage per hit on the Druid Tank: 4.16m
Although I’m in tank spec for both and Brann is exactly the same, that’s well over 100% more damage for Brann on my Monk Tank. The question now is why is that? Is this a bug? Or an intentional effect? In any case, the result is that the Underpin on ?? is almost trivial as a monk tank and considerably harder as a druid tank. I think it will look similar for other classes/specs, making the delve boss almost impossible for some or at least requiring significantly more tries.
It would be nice if the devs maybe could look at this and explain to what extent this is intentional. I can hardly imagine that it makes sense that delves are much easier for some classes solely because Brann does 100%+ more damage.
The post should only be seen as information for other delvers and as a note that there are still many problems with Brann and not as a rant. I am completely fine with the difficulty, also in my opinion it should be the same for all classes with a certain specc (tank/heal/dd)."
Other players pointed out more information leading to the following:
"Branns damage output seems to be constant for Prot Warris, Blood DKs and Monk Tanks with around 1.5m DPS. For Druid Tanks his damage is strangely halfed to around 730k (as also described by others here). This might be the case for other Classes or Speccs as well. For me this clearly looks like a bug, which should be adressed. Especially with the new harder delve mode being around the corner in 11.1.7.
Brann seems to scale with the players crit (and likely also versa), which can lead to some (but not all) of the different damage. Maybe a good solution for this would be to change Branns scaling with the player on base of the ilvl and not on actual stats (where haste/mastery don’t have a big impact)."