So, when you are tanking (as anyone) you want to balance armor, MR, and HP to most efficiently increase your effective health. To make things simpler, say the other team is mostly physical damage. Say you currently have 2000 hp; in a team fight with your ultimate on your effective health will be multiplied by at best 1.5, not doubled:
Originally Posted by NessOnett
So having nearly double health every fight is a bad thing?
Thus you have effectively 3000 health. Now say you buy a giant's belt (which gives you more hp per gold than warmog's). The giant's belt gives 430 hp, which increases your effective hp by 430*1.5 = 645. Instead, for the about same price, you could buy about 70 armor (based on armor per gold of a chain vest). Each point of armor increases your effective health against physical attacks by 1%, so your effective hp would be 1.70*3000 = 5100, a 2100 hp increase.
2100 > 645
Now obviously this is an ideal case and the calculations are rough, and you'd usually have to get armor and MR, but the point is pretty clear. Not only is hp stacking less effective, but makes you more vunerable to hp based attacks, like other mundo's cleavers and DFG. Your passive also scales with hp, but health regen is more important early game (another reason not to get warmogs), and the same argument applies anyway.
As for DPS vs. Tank Mundo, I usually build similar to Pwnacus. If others wanna build tank, that's fine by me, haha, what bugs me is when ppl get on my case in game for not stacking warmog's. Disregarding armor pen, etc. DPS = dmg*(attack speed)*(1+ crit chance), so the more dmg you have, the more valuable crit and attack speed are, and since mundo already has a lot of damage, I usually avoid inf edge and blood thirster and go for starks and zeal/PD, but again, whatever floats your boat.
Lastly, for those who play tank Mundo, I will usually just ignore tank Mundos and go after the squishies, how do you stop this? If your answer is by attacking back, wouldn't you be less ignorable with more damage?