I'm wondering what the mentality is behind this?
I read that there is a divide between the 1/2e era and 3/4e era DMs and players. This isn't a universal, but-
Huh.
I think a lot of it comes down to viewpoint. For example, if I was playing a character, and due to some quirk in the rules it became evident that my character was "broken," then I would discuss with the DM how to fix it ("nerf") the character- and I'd be okay with that. And I expect that when I DM, players using 3PP (UA, other materials) do the same.
I do not think that it is, or should be, the DMs job to "compensate" for broken characters by throwing stuff at them. IMO, that just compounds the problem, and becomes an escalating power war. But every table is different, I guess.
Undying light Warlock.
Two issues-
First, great concept as sketched out. But it really needs more ... fully developed thoughts. There are some on-line resources (which you can look up) that do that by changing out some of the spells, etc., but it's a great idea that needed a bit more work.
Second, you can't have both an Undying Light and an Undying Warlock. I mean, c'mon. There's a lot of words in the English language.