Atmogs would be a much better alternative to Shurelyas. Sure the movement speed boost is nice, but let your support/tank get it. The only truly useful stat on that item is the health bonus. But if that's all you want then get another Warmongs.

With Atmas, your AD is increased by a whopping 80 with your endgame health. It also has a nice amount of crit and armor.

Also, going 9/21/0 in masteries would also benifite you more in your "Tanky harassment" role. The magic pen works with your Cleaver and W, and you should never overlook that 15%.

As with your build right now, Mundo will do little damage in team fights. And will be easily ignored until your whole team dies like that Cho Gath walking around with 5 Warmongs and 9k+ health.

I wouldn't think of tank mundo as a backdooring champ since it is gonna take him forever to take the tower down while at the same time leaving your team without one of its members. If you want a backdoor champ go for yi that **** is just ******ed

Unless it's for quints, hp/lv is far better than flat. For example, your yellows give 45 hp at lv 1-18, okay. hp/lv yellows would give 10 at lv 1 and 175 at lv 18. This is a big difference.