is this a Bug of Feature?

Hello Everyone, Scarlett witch has a ability that lets her be invincible right?

But with multiple Abilities in this game (most easy to replicate is the Ult from Psylocke or Spiderman Uppercut combo) if you use the ability right as they start up the Attack you still get hit 1-3 Times before the game recognizes your invincibility. Is this a bug or intentional ?