Hm.
I recently noticed that Miltank has been denounced to the RU tier, I have to disagree.
Why?
Miltank has been one of my powerhouses for a long time now. And believe me, the best set she can run is:
Miltank
Ability: Scrappy
Nature: Impish
Item: Leftovers
Moves:
-Seismic Toss
-Milk Drink
-Attract/Heal Bell
-Thunder Wave
(252 HP Evs/252 Defense Evs/4 Speed Evs)
She is the Ultimate physical wall, and can even handle some special-oriented Pokémon. If you like having fun, the use the ParAttract combination to hax to death your male opponents, or if you prefer a safer option, stick to Heal Bell and fill a more supportive rol. Anyway, it works wonderfully in OU, so try it!
I've been using a set identical to this and it works wonderfully. Using Heal Bell, of course.
My EV spread is different (focused on both defenses and HP), so there's that.
However, after using Miltank in UU, I've found that it more or less stalls out the entire UU metagame.
I didn't copy it before, nor did I notice it before looking at this thread now, but Miltank really is a beast when you use a set similar to that.
Seismic Toss has
no resistances, making it much more effective as a offensive utility than Chansey. It's no setup fodder; 100 hp hurts most substitutes in UU and is no laughing matter.
Of course, it has its faults (Chansey tends to be really annoying), but it can take Focus Blasts (reason to have Special Defense buffed) and strong fighting moves to the face. (reason why it's also a very effective mixed wall)
Basically, if you aren't prepared for Miltank, be prepared for probably the most effective offensive medic in UU right now. Yes, I'm even calling out Chansey as it can't go on the offensive quite as effectively.