Jarvan IV is playing to strong with a lead

I know Riot tries to allow for teams to bounce back when another champion is fed, sorta to diminish the "this 1 champion is fed and carries 1v5", but Jarvan isn't anywhere near that. Ahead, he is doing so much damage to those trying to tank against him to bounce back and those who are squishy like Lux. Being that she is a burst mage, he built just Merc's and sustained through ALL of my damage. Teemo couldn't even shred him down.