There is no change. The Mist Dragon involves mechanics that aren't as easily telegraphed as "Hey, avoid these huge orange lines/circles". Any team aware of them will smash it just as easy as any other boss, and when overgearing becomes a factor it'll also be done quick enough to avoid a phase entirely.

The Alphascapes are the same deal. Neither A1 or A2 were much of a challenge blind for me as a Healer (and blind/inexperienced Healers can be far more detrimental than blind DPS) - A3 was only awkward due to blindly having to realize that his beams are the same Fore/Aft / Port/Star spiel from the old Relghar's Fist dungeon (2nd boss), except the beam cuts across 75% of the arena and hurts like hell, as well as the fact the boss will do it twice and try to confuse people by spinning before choosing left/right. I had to get through it blind with pure guess work until I realized which beam-description meant left/right, and simply positioning appropriately. The rest of the mechanics are easy to pick up with trial/error.

TLDR - It's not that they've become 'more difficult', it's the fact that people just haven't adapted to the mechanics, and said tier has arrived along with new gear. You will see that difficulty magically disappear when people learn the mechanics and up their gear. Even without said gear, the Burn has been smooth sailing due to everyone having had some time to learn what it's all about. Only my first visit incurred wipes.

https://www.youtube.com/watch?v=3ySbYwjH32k

Eg. I'm playing far from perfect and we had a DPS DC leaving it 3.5 v Dragon, yet at no point was there any major danger due to people (mostly) knowing what to do. It is most definitely my favourite dungeon-boss addition in quite some time... But difficult? Hell no. Same applies to the Alpha's -- and almost ANY new content where you have to tackle it blind during a new gear-tier.