I think Atma's Impaler could be switched out for another item that gives greater armor for ground slam. Also adding a few items that give ap as well as armor wouldn't hurt such as a sunfire cape or zhonya's hour glass. Sunfire cape could replace your atma's impaler since with only 2199 health and 2% of that turning into attack damage comes out at around 44 extra damage. While sunfire cape only dishes out 40 itself it can hit multiple champions in the area and it gives you 450 extra health with the 45 armor. I think zohnya's hourglass would help as well because it has a nice active to save yourself with in a tight situation. I know you said you don't use actives that often, but it would be a nice touch if you added it for those that did. It also gives 50 armor (5 more then atma's impaler:) ) and 100 ability power which gives your ult an extra 100 damage in addition to your ground slam ability doing around an extra 250 or so I believe.

Otherwise good build!