Combat in 3.5 averages at like, 4 rounds, even for a boss fight. With the 1st, maybe 2nd round, deciding the results of the combat.

Indeed: there are spells (Phantasmal Killer, Baleful Polymorph, Dominate Person, Power Word Kill, Banishment), that ends combat in a singular turn.

You're right in that 4e combat was much slower and purposeful. I'm... neutral to this. I can say that 3.5 / Pathfinder 1.0 combat is unusually brutal... to a non-intuitive degree. 3.5 / Pathfinder 1.0 heavily relies upon resurrection magic in practice due to its unusual brutality.