This is an important question, for wintertide trolls I can only pull 3 or maybe 4 depending on the group because of their knockdown. The ice area I can pull 5 at a time and generally be fine and the fire area I can pull 4 or 5, but all my party members die from the aoe so it's more realistically about 3 maximum at a time. The ensign area however, in certain groups I'm sure I could pull every enemy in there and still be fine, in the average group it's more like 7 or 8 as my limit but honestly it's not even worth pulling that many at once so I usually don't. If these numbers are intended then it's already balanced, but I'm sure the ensigns at least are not.
This happened in a group I did today at ensigns. If I was playing my dps build there's no way I would have ever pulled more than 2 at once, but in my tank build I was regularly pulling 4 and a couple times accidentally got 5 or 6 and it was still perfectly fine. The biggest problem became the constant chain stuns even with 60% stun resist and 55% ranged + projectile evasion, which meant I couldn't keep up aggro occasionally. But even then, I think there were only 1 or 2 deaths in what was a relatively weak group since we only had 4 people for a time, and of those 4, I think only 1 had a completed build. In other parts of the dungeon, I think I was pulling maximum 3 at once intentionally, but we could still handle 4 if another came by accident. So I guess going up from 2 at once but still dying sometimes if I ran dps, to 3 or 4 at once and rarely dying, but lower damage is reasonably balanced. Maybe a tiny bit too strong, but bearing in mind, although my build isn't complete, I do have all my mitigation mods. I'm only missing some aggro and damage mods and it is mostly max-enchanted yellows.
I'm honestly just glad it's relatively painless to make a tank build now and I've definitely already seen more people using them. The last thing I would want is for them to become useless unless you have a perfect build like it was before.
So, I think the biggest problem is the passive darkness mitigation mod that unarmed has. After doing a couple more runs with weaker groups, the other parts of the dungeon actually felt reasonably well balanced to me, but it's definitely preferable to have a tank in the group now, rather than an all dps group in every situation I would say. Whether or not that's an issue I don't know, but some people might see it as "forcing" groups to have a tank.