This is an issue I noticed with the new system, as well. Basically once you get hit, you have a significantly lower chance of making a comeback from the situation if you're not in plate (or have 140 up) and capable of tanking through the whole thing. Before, even in lighter armor types, you could fire off your emergency skills or otherwise still manage to last through the initial stun/round time and escape a reasonable amount of time. It may not be an actual bug, but just an unintended interaction in the new system. Similarly, lowering everyone's defenses means people are getting hit more (at least with more common stuff like creature maneuvers), seeing higher end rolls on those hits and then being subject to the above steamroll phenomenon you described - basically, more interacting mechanics that compound and exacerbate each other.
Players don't like to feel helpless. They dislike these new dynamic the same way they dislike getting insta-gibbed by a single charge maneuver or stacking round times (which feels more prevalent now, as well) in the older system. If the code on the backend is working as intended, then it might do good to either raise everyone's baseline maneuver defense back up a bit or lower the penalties from stun/injuries/whatever somewhat. Maybe a bit of both.