Slag is a somewhat clumsy mechanic; I’d say the reason TPS handles things better is that cold is a more interesting debuff mechanic.
As for people not understanding the different playthroughs, all I can really say is “what subgenre do these people think they’re in?” My understanding is that this design model of multiple playthroughs, with a significant difficulty step at each is standard and arguably part of the definition of the ARPG subgenre.
I’ve been playing Grim Dawn for the last several weeks, and they do exactly the same thing (they call their TVHM “Elite”, but Normal and Ultimate even have the same names as here ). The difficulty step seems to be mainly on the damage-taken side rather than on the damage-done side like BL2, but same idea. The only complaints I see are of the “I would prefer only two playthroughs to reduce burnout from repeating the same quests over and over” variety, which I agree with, but this genre likes triple repetition so it is what it is. Well, except for TPS with their de facto 4+ playthroughs due to borked UVHM xp, but that’s the reason so many of us bail on TPS in early UVHM…
I’ve seen people refer to BL2 as a FPS rather than an ARPG, so if they’re coming from that direction I can understand the confusion. Probably. I haven’t played FPS in literally decades (1995, I think?), but I can believe that three playthroughs/difficulty steps is not a thing over there.
In an ideal world I’d like for these games to get you to level cap in one playthrough, and you set the difficulty separately when you create a character (I think of this as the Mass Effect model, since that’s where I experienced it). But that either requires a truly massive amount of content, or a very very fast character progression, so I can see why most games don’t do that. And since ARPGs are also all about loot-farming for top gear a significant amount of repetition is already baked in, so looping through the story a couple times is a reasonable solution to maintain a normal pace of character progression.
My sympathy for this is largely limited to people like knighm, who gets roadblocked partway through UVHM because he’s 70 years old and has even worse reflexes than the rest of us. Otherwise, if people want those last 22 skill points they need to adjust to UVHM; if they don’t want to deal with UVHM they don’t need those skill points.
This “auto slag” nonsense is indistinguishable from someone simply editing their character to be level 72. There may be ways to do it, but I don’t see why anyone should pay attention to these people.