uh are tier-3 delves supposed to be harder than Heroic dungeons??

I'm having a hard time soloing them on my mage, if I don't wait for Icy Veins on every elite mob pack

I would have thought tier-3 would be braindead easy, considering it goes up to tier-11?? and I certainly did not think it would be harder than Heroic dungeons

am I missing something? how dang hard is tier-11 going to be then...