Cathedral of Flames Path 1 & 2.

Path 1 contains a lot of skippable content (run straight over bridge) and content that can be narrowed down (Just kill acolytes, just kite mobs until acolyte respawn).
Path 2 is much the same, not exactly skippable content but with a bit of organisation a lot of the events can be handly easily (Chain-kiting mobs until door gets opened, position to pick up bombs before starting timer)

Honour of the Waves Path 1.
This path contains no complex boss fights, and the final boss can be killed easily using a specific method.
Ther're a lobby before the final boss room, if you stack up on a bit of plank coming out of the wall to the right of the room, one person pulls the boss into the lobby and underneath the stacked party, from there he can only do small AoE damage while you just wail on him.

Ascalonian Catacombs Path 1.
This path has a few annoyances, but with a competant party it can be done easily.
Skip the lieutenant. Bring lots of stability for versing Stalkers. Final boss is tank/spank.