Will PoE2 be slower?

YES!!!!

It will be slower than poe1 as there's so far we not seeing any movement speed flasks and not much movement skills.

Mobs killing will be slower as well cause we start fresh and we don't know what uniques are available, I'm sure the leveling will be much faster a month or 2 in when leveling uniques are wildly available, the first character though the leveling through campaign will be painful cause of dark soul like game play and probably gonna turn some people off if they are used to Poe 1 and Diablo 3,4.

It's kinda like Diablo 2 new league character you will need to get 2 levels above the zone and farm before progress to next boss etc