According to the main menu, skulls are awarded for completing missions or multi player matches. My issue is, that I'm not being awarded any skulls for completing campaign missions. I'm just finishing up a second campaign run ( Full Campaign Reset ) and am only getting skulls when Elites reach their skull award level tier, lvl's 2, 4 & 7 I think it is.
I've also re-played lots of missions and am seeing the same thing, 0 skulls for the mission itself unless an Elite hits one of the Xp tiers that awards skulls.
In total, I've played enough to get 10 elites to level 10 and am sitting on 140 skulls, 100 of those are from the 5 1v1 games I've played.
Is anyone else experiencing this?