Well i did it, built a pure DPS Dr Mundo. Got the most kills I ever have in a LoL game, 19-4. First got HP regen for cleaver spam, then berserker greaves. Infinite edge, phantom dancer, black cleaver. At low HP with just the infinite edge I was crittin 1000 dmg. I was 2 shottin champions.
The ultimate is totally pre-emptive, use it going into battle, then when you are close, dmg buff, cleaver slow, dead. I rarely use the aoe attack unless im farming.
This really only works consistently with a good team, if ur gettin owned its better to get HP.