I am almost 100% certain this is not intended. I discovered this using a combination of Black Knight and Lightsworn. When the two are on my team (4 or 5 in any setting) one of Lightsworn's abilities will remove a buff granted by Black Knight one turn earlier then intended( I think). To keep things simple Lightsworn(LS), Black Knight(BK), and random other champion(ROC) will be abbreviated. 

LS will use his A3 granting 2 turns of 60% increased defense and a rez. effect to all allies for 2 turns. 

ROC will take his turn. He ends and the timer on both of the buffs granted by LS will go down to 1 turn.

BK will use his A2 granting all allies a 15% continuous heal and a 30% increase defense buff for 2 turns. (NOTE: The 30% increase defense buff does not show as an additional buff on all allies. As I don't know if you can have both a 30% and 60% increase defense buff simultaneously this may or may not be a bug.)

ROC will take his turn. He ends and both of the increase defense buffs are gone entirely. The while the 60% increase defense buff has run out of time the 30% increase should have one more turn according to the ability description. 

Therefore, I believe that this is a bug that unintentionally strips away the buff one turn early because of the similar buff ending. I dont know if this applies to other stat buffs (ie attack, accuracy, etc.) because I only have this combo to try. This happens 100% of the time though. 

Kind Regards,