Control over the size of that window
As to why we think resilience needs to reduce crits, it is because you are playing against another human and not an AI-controlled creature. Creatures generally do not heal or blow defensive Mortal online gold, or at least not very well. The ability to pack a lot of damage into a small time window is much more important in PVP just because the opposing player or team have so much control over the size of that window.