Were you trying to play at or near release? Because it's an almost universal truth these days that Day 0, 1 and maybe 2 are generally just shit for performance.
FWIW, when I clear past these weird connection issues (I assume GGG is doing some sort of queue system), most of my night is problem free after that. There's some weird latency spikes at around 3am to 6am (when I uh, should be asleep) but I assume that's just server maintenance and the # of servers in the clusters going down.
So generally since Lockstep, I'd call PoE's performance "good" overall, with some quirkness.
That said, I don't have a build that generates lag and I know that's not true for everyone.
I suppose if/how they retune Malachai's fight will factor in also. If he morphs into a near-faceroll fight (the way Piety and Dominus did before him), no points will be won with me.
I'd expect these fights to get tuned down, hopefully. Merciless Dominus doesn't even really bother me anymore, as tedious a fight as it is. What I REALLY hope for that is you don't have to kill three goddamn bosses every time you want to go fight Malachai. That fight is bad enough already without having another 20 minutes added on to the front of it, and the risk of a total reset if you DC.