I’m not sure if this is by design or not, but now after leveling a hero, you see the screen that displays the hero’s card and says “Hero Leveled Up!” When you hit ok, you go back to the Level Up screen where you can add additional feeders. When you are done there and click the “x”, you are then shown the hero’s card again. You have to hit the little “x” at the corner of the card, which is not in the same place as the big “x” from the previous screen.
This second viewing of the card really doesn’t add anything, just the tedium of clicking it away. When you are leveling heroes with a lot of feeders, it gets old very fast. It makes the whole process take longer for no real reason.