I believe Stoneskin shows debuffs as blocked.  Leos passive probably does the same.  The ones not in Stoneskin I'm not sure what would have caused it.

Ya stoneskin i know, shows debuff blocked, just it showed on arbiter and leo thats what got me curious, as they werent in stoneskin, ive never worn immunity set myself but i understand it still gives you a visible buff at the start of combat, they didnt have it.

Who knows xD but one more random occurance, which i today had too, is the opponent instantly getting killed after the poly HP is beaten down, the opponent should come back as real self with half hp, but ya, couple times has it happened, just insta death.

That one is a multi hit thing.  1st hit pops the Poly and 2nd kills the champ.  Looks odd visually when it happens though.