Stop with this myth. DUNGEONS WERE NOT SACRIFICED JUST TO MAKE ULTIMATE.

YoshiP explicitly said that wasn't the case. The removed dungeon resources go to all sorts of places - he mentioned the 4.1 solo duty as an example of something they wouldn't have been able to do, so figure the 4.3 duty is like that as well. Resources also likely went into Eureka, the fancier look of HoH and perhaps more engaging fights in there, maybe even a little to Hidden Uznair etc.

Designing the three bosses is only a small part of the work involved in doing a dungeon. You also have a boat ton of visuals to put together, you need lore for it, writing the quests and any in-dungeon text, figuring out what the trash is going to be and making all of that, and QA resources to test all of these things with a fine-toothed comb.

A dungeon is a huge endeavor, and the payoff just isn't there. They would have dropped the dungeon whether they were doing Ultimate or not.