I found the lack of AoO quite refreshing, actually. My monsters were dashing in and out of combat, they were able to escape battle to try and gather reinforcements, and they were constantly mobile and shifting around. My PCs wound up doing the same; they chased down fleeing creatures, they ran around, ducking in and out of cover.
Despite the freedom of movement, it always felt like the PCs could still enforce crowd control. In the narrow corridors, they were able to form a two-man wall and block the monsters from getting past; it was a very effective tactic. And the interrupt disadvantage-tanking was used to great effect.