A good way to fix this new save throw system is, every time u hit the enemy's armour, there's a chance for they to fail the save throw check so the CC kick in, chance is decided by how much damage u make against their current armour amount. So for example if the enemy has 100 magic armour and u casted a fireball which cause 50 fire damage, there should be 50% he failed the save check and got burning status. If you did 90 fire damage, the chance will be increased to 90%. And no matter how low the damage is, there should be a 5% to success, just like other classic d&d games.