I disagree. And rather, I'd point to what you just did here as an example of what I mean. As I said, it OBVIOUSLY made something simple that was not AS simple before. Yet here you give a perfectly logical...but entirely "dodging the issue"...explanation to try and categorize it in such a way as to NOT call it dumbing down, when that is, in fact, what it did. It wasn't (and still isn't) a "read the tooltip" ability. Most people don't understand that it only requires restoring HP equal to the DRK's total health, not restoring the DRK to full health, for example. A confusion easy to make considering several Doom effects in the game work that way (dispelled by reaching max health), so it was an easy mistake to make. Further, logic would make people think the effect wouldn't EXPIRE (the unkillable effect) just because the undeath effect was removed. Yet it was so.
There was quite a bit of nuance to using it correctly. As it turns out, party coordination is a kind of skill, thus related to skill ceiling. But more than that, knowing those effects was the difference between knowing when and how to use it correctly and not, which IS skill ceiling.
I used that example because it was a GOOD example.
I don't think complexity is tied to skill ceiling. There have been some Jobs with complex rotations that were, nevertheless, somewhat easy to actually do. Conversely, there are some Jobs that are mechanically simple, yet have a high skill ceiling. BLM is mechanically simple. If you ever sit down and look at its main use rotation in a vacuum, it's one of the easiest in the game - something BLM mains often say themselves. It also has one of the lower APMs of all Jobs in the game. Yet it's seen as having a high skill ceiling.
That is, complexity isn't even connected to skill ceiling. While in theory, logic would have one think that a more complex Job will have a higher skill ceiling, this isn't ALWAYS the case. While the two can be correlated, complexity doesn't cause high skill ceiling, nor does simplicity deny it - if it did, BLM would be an easy Job.
.
Now, we can talk about Dark Arts on the side, but again, this is proving my point:
Changes that people like (Living Dead) are justified while changes people did not like (Dark Arts) are condemned, when both are examples of dumbing down.
A second piece of this is that people tend to focus on DPS rotations AND NOTHING ELSE when talking about complex Jobs for the most part. Which is also the case here (LD vs DA). There is one particular exception to this, but only one in FFXIV I'm aware of, which is AST. AST has the easiest rotation in the entire game, and is the only Healer that has only two DPS buttons (Combust and Malific), yet is considered complex and with a high skill ceiling despite this. But for every other Job, people look at DPS rotations and kind of ignore everything else, including Tanking CDs and the like. Which is also why LD's change isn't considered dumbing down, despite being dumbed down.
...but I think the main reason is because of it being liked.
And I don't mean any of this as an insult. I just think it's a great example of how much people pick and choose what forms of "dumbing down" are and are not acceptable to them; partly by choosing to define things that they like as not dumbing down even though they very clearly are.