How is a single hard encounter taking you four hours?
1/2 RP a session, 1/2 encounter. I don't go, okay guys, 1, 2, 3 roll! 1,2,3 roll! Players try to assess the situation they are about to enter, and come up with a plan, it isn't all move in, attack rinse repeat.
This is even with my house rule of requiring a reaction to talk when it isn't your turn in combat with something that could take up to 6 seconds.