Came here hoping this thread would exist, and it does, which is great.
This change is awful for everyone who tried to do everything above-the-board, and the initial reaction from the people behind the tool that prompted it was just that they'd make a version that everyone can run that just cheats locally with client-side way marks. It's ultimately not going to get people who were using this tool to cheat to play legit, they're just going to cheat harder. The people who lose out are literally the entire rest of the playerbase who persist in not cheating, and that's not great. Adding more waymarks so people can just pre-mark everything is an option, I guess, but it's a lot messier visually and it's open to way more abuse (There's a clear waymark button--you don't think that's 'accidentally' getting hit right before a pull in 24 mans to troll everyone? Really?)
I appreciate the urge to crack down on the growing prevalence and unfortunate acceptance of tools that allow for automation of what were intended to be manually handled game mechanics, but punishing the people who were doing it right in the first place is a bad look. As mentioned in the OP, people who can place way marks while keeping up with the demands of their job mid-pull have a valid skill worth recognizing, and instead it's getting wiped out. The community will adapt to the change, but given the existence of things like the tool that would place party markers on people for Titan Gaol, the precedent of 'cheaters abuse it, so all will lose it' could eventually scale out to touching other features and it really, really doesn't need to.
We should absolutely have at least one way mark we could place in combat, for on-the-fly positioning explanations. Yes, it's open to abuse by third party tools, but the people using those for hardcore early prog aren't going to stop using them with this change anyway, so why punish the rest of us contentedly progressing slower without the assist?