Pushing this many changes at once will shake combat balance a fair amount, I don't think that the usual 4 weeks of PTS cycle will do for a good amount of testing.

Given that the combat team seems to care about the state of the game and want to improve it, I fear that pushing this many changes in such a short time-span is overwhelming not only for the playerbase, but also for the team. They're not gathering enough data to make the correct decisions.

In order to illustrate what I mean, I'll give an example, they wanted to include the Oakensoul ring in the High Isle chapter, but they clearly didn't have enough time to develop a balanced version of it before they had to drop it on live. Then, after a lot of players spent their money on the ring, they nerf it quite a bit, causing bad feelings and distrust amongst the playerbase. (Even if the new version is still quite strong but not broken.) If they had dropped the High Isle PTS earlier or beginned testing the Mythic in prior PTS cycles, they would've released a strong but not broken version of the Mythic since chapter release and the community's dialogue would be way different right now.

Another example: Stamsorc damage is overperforming in both PVE and PVP in the High Isle patch. They are nerfing it to the ground in both PVE and PVP and pushing Magsorc even deeper. I don't believe that there's gonna be enough time, manpower or data to balance out the class before the next patch drops. Not with all these other changes to keep an eye on. We could've started with a couple of tweaks here and there and then proceed further if needed, adding further nerfs as the PTS patches progress. This will likely leave Sorc mains very unsatisfied for a complete patch at least.

TL,DR: Pushing raw and incomplete changes to live, because of the current schedule of the PTS cycle, isn't a good thing for the game, changes should be thought through and tested thoroughly, otherwise the game feels like it's stuck in Beta forever.