I have the impression that large monster groups behave kind of stupid in RTL. With my playgroup it happens very often that a large monster is blocked either by its other group member or by small monsters on the map. It is wired when a (supposed) heavy hitter can't attack because a zombie is in the way. This is mostly because the app often calls for engaging a certain hero and that leads to a huge mess in narrow corridors.
I guess it is up to the players to help the non-existent OL out and place monsters smarter right?
maybe it's just me?