Let's be honest people complained about it because they didn't know how to deal with regeneration.
It was quite hard to deal with regeneration when most of the things that were supposed to deal with it didn't work and the only thing that actually stopped it were adamantite weapons, of which you would be lucky to have found 2 by that point, and then had the random foresight to bring them along.
And at the time most people haven't yet figured out/come to terms with how ridiculously overbloated AC would get in the game, so no one was thinking of building daisy chains of half a dozen feats just to be able to hit things. Before blackwater, the standard D&D vidya gnome plan of wear good gear, cast some basic buffs plus haste worked on everything. And going there early in the chapter was the wall where the full extent of owlscat's autism dawned on you.
That is not mentioning that the place was indeed nerfed since launch.