There are multiple ways things that happen “on skull hit” are processed. Without going into too much detail on this (again), Psion’s mana drain happens before (and independent of) damage calc (because it drains mana even on lethal skull damage; entangle/0 attack blocking it is a special case), while status application traits only process after damage is actually dealt (because they won’t apply if no damage is dealt, so they obviously have to know how much damage is dealt). They could be clearer about where these lines are, but it is unlikely for them to “fix” this issue by reordering the way things are resolved and risk breaking a dozen other things.