Sorry to dredge this up a bit, but since this is really the root of part of the debate at hand, the difficulty curve thing is actually worth addressing in detail really.
Whilst I personally think Pharos Sirius a fun dungeon, I do also think that the nerf calls were warranted in some respects, the pirate boss threw debuff stacks like candy, the bird boss just confused people as to how to deal with it whereas Siren would have almost been perfect if her dash/donut move was just a little bit more forgiving (Or /gasp, choreographed).
Rather I'd like to bring the original Amdapor Keep to your attention. That in my opinion was the perfect expert dungeon. Why?
it wasn't excessively hard or complex, I'd argue that the current crop of dungeon bosses are far far more technical than what we had in AK back then. Rather what made it a fantastic dungeon was that it copied and drilled you in key mechanics that you would later need to deal with Titan HM and Garuda. And by drilled I mean that whilst the mechanics were pretty simple, the dungeon wouldn't let you slack off. If you ignored stuff, it'd kill you or cripple your healer's GCDs whilst they fight to keep you alive.
Compare that to Skalla where it's really quite viable to just ignore a very significant percentage of the AoEs and such.
TLDR: AK taught players the foundation of skills to deal with Titan HM, Kugane and Skalla teach people that it's very viable to watch another screen whilst mashing 1-2-3.
The perceived difficulty of 4.0's primals is somewhat irrelevant really, the issue here is the disparity between them and the expert roulettes. Those dungeon's don't need to be harder, they just need to show players relevant mechanics in a manner that makes them pay attention.