I haven't had any real issues with the servers so far, just a little bit of lag here and there that's probably on my isp's end.
However, the HP scaling in Torment 1+ seems to be completely insane. Torment 1, fighting a certain miniboss, my Barbarian was level 65 at the time, and the boss had over 330million hp, according to the health bar readout. That fight easily took 15 minutes on my admittedly lower-end dps barb( about 150k at that time, bad luck finding weapons).
Also, Act 5 seems to be AoE or go home. Every other creature spawns 4-10 of smaller creatures, and there are a few chain spawner scenarios where you can end up with dozens of trash mobs running around, soaking up damage. On the plus side I do see a couple exp farming strategies in the future, when you have some decent gear.
Got to level 69 before I had to take a break and go get some exercise and dinner, DPS is up to around 260k now with 2 socketed 1handers(rares, no good legendaries yet). My drop luck seems to be even worse than 1.08 so far.
Easily the most dangerous affix seems to be those homing Ice shards, that not only start doing damage instantly when you are in the radius, but they also slow then freeze you even as you start running. Those + vortex + waller or jailer = usually a death for my Barb, even with 280k hp, 800 all res, 78% armor reduction. Not sure if the damage portion of the ice is bugged or what, but it's way higher than the poison/fire damage affixes by far.
The maps so far have been pretty good, packed with creatures once you get past the very first act 5 zone. There seems to be a lot of side areas/mini-quests available too, I've been going for a complete clear of Act 5, but you can definitely speed through to the mini-bosses/boss if you wanted to.
Barbarian definitely feels weaker in the expansion than vanilla D3, but that's partially due to my generally shitty equipment as I level. Avalanche is beastly though.