I have really enjoyed some of this game and at times loathed much of it. For me Halloween aka Mad King was fun. And that's where I had an opportunity to look back at the old vs the new.
Mobs are losing their identity. What I mean by this, is every mob has some form of a ranged attack and can be tough in close or far range. I really don't like this particular change to NPC's in general. There should be a diversity of close combat mobs and ranged mobs that don't intermix. This allows player to utilize their weapons/ skills to the fight, if all of the mobs hit hard no matter how you fight them then it becomes a race to do the most damage.
Too much projectile hate. This just goes for mobs and many special abilities that are outright broken. For instance smokescale/ smogscale/ dust lions all have some for of an AOE projectile field that no projectiles can hit them in it (even when your outside the field and not affected by the blind). A veteran Smokescale can one shot a full health character with it's opening attack. The abilities have long durations and little downtime. Dust lions added long duration knock downs to this annoyance. Though to be fair their field isn't as long lasting as the smokescale.
Every awakened undead applies slow/ cripple combo for super long durations. Not to mention the one that bursts out of the ground and can down you in one attack since knock down takes way too long to recover from.
Look at two condi's they buffed torment and confusion, and how many of the new mobs use those particular condi's.
I'm concerned with the constant escalation of damage and health of mobs. And this leads to a massive balance problem with the entire gameplay, Veterans that are worse than champions is now a here to stay problem (you can thank HoT being about group play for that one), but it's not just there you can find basic mobs that put vets to shame, then there's champions that are worse than world bosses. It's really starting to feel like there is no balance or more accurately keeping the mobs in check when it comes to gameplay. I would like to see a return to some semblance of balance and mob type, though at this point we already have had an entire expansion where this was ignored.
I enjoy the game for much of the time I play and this is where I'm torn. If I quit, that's it. I won't come back as nostalgia for the old isn't what I like spending time on.
I do hope this game does get back to basics with less muddying of the water, only time will tell. Better gameplay should be more important than a new shiny.