I implied that 2 of the eureka areas that were cut were replaced with some of the things I mentioned.
None of the Eureka areas had Critical Engagements. What I explained about them involving the same sort of work as dungeons bosses is important to consider. In eureka we effectively just had skirmishes, which is just make a mob bigger and more powerful and call it a boss. There was sometimes mechanic work but I don't think it was on quite the same scale for most of them except the big one in each area like pazuzu. The critical engagements have the sort of mechanics we would expect in dungeons and raids.
And of course we didn't have a Dalriada, a Delubrum Reginae, DRS, firmament or ocean fishing areas. You can argue that level design work from eureka transferred into all of these extra things but the boss fights and mechanics would most likely lend work from the 2 extra expert dungeons and the deep dungeon fights that were cut.
I think that the Allied beast tribes, the ultimate and holiday events were cut because of covid. I am guessing on the Allied beast tribes and holiday events, but if I was a producer it would be a pretty obvious decision to cut "small" things like holidays and allied quests to make up for covid backlog. They've never cut holidays this way so it seems pretty obvious why.
The second ultimate has even had a lot of work on it so it's not really fair to say that this was cut for other content, it's been said it was done because of covid backlog getting in the way and needing to prioritise the expansion.
I have no idea how some little Tataru outfit can come into this. What is that even about?