Courage of the Colossus is broken on certain characters

This mastery is insane on some champions. The fact that it stacks up to 5 times on what is already a really strong base amount is ludicrous. The main problem is that a lot of champions with hard cc were not balanced with this mastery in mind. Gragas should not have access to a 2000+ health shield when he jumps into your team. I think that the shield strength should be lower, but the shield duration should be higher to compensate. Maybe 5% max health for 6 seconds. When taking into account the 5 times stacking thats 10% less max health from your shield, but it lasts 50% longer.