It really is not necessary for me to post this, but since HV is so stupidly slow right now... ----
Technically speaking, there are no difference between any of the Specific mitigation, so grouping them separately as 'Specific
physical/
magical mitigation' can be misleading; after all, MM does Pierce damage.
QUOTE(buktore @ Sep 18 2012, 13:55)

The Damage Type, or the Element of an attack, is irrelevant to whether the attack is Physical or Magical, so all the elemental strike, while sounded like a magical attack, you're still attack with a weapon, hence still a physical attack.
In fact, the game itself considered the 4 main melee damage type (Crush, Slash, Pierce, Void) simply as yet another type of 'Element' and treat them identically to those of the real element— it even labeled them as such internally...