Just finished the game for the first time and i must say that Act 4 was a major letdown....didnt feel to be in tune with the rest of the game.
the quests you get from the gods are each done in a matter of minutes + travel time
cant exactly put my finger on it but after descending the pit i was expecting an epic dungeoncrawl and not a "run through in 15min with some minor trash mobs" experience leading up to Thaos. thats kinda symptomatic for the entire act...just feels cheap and somewhat rushed compared to 1-3
also, imo, the Thaos fight has waaaaaaaaaaaay to many loss of control effects ... attempted it numerous times and more often then not half my party was dead from the first hit from the judge despite trying like hell to get away from melee...
and then theres the actual ending...10min. of narration and thats it...it just doesnt feel like you've accomplished something big...sure, the narration tells you otherwise but the feeling after defeatint Thaos is just kinda...meh...
oh, and for the record, without reading a lot of the non-main quest stuff it took 29h....