So I just went with this:

Merc. Threads
BC
Iceborn
Locket
Shurelya's
Scimitar

And...at this point I don't think it even matters if you build damage, you are going to pwn someone if your abilities are up.

This champion is going to get nerfed. So enjoy it now boys and girls. No one can hang with her top, and she can jungle well. Her health is bananas strong, and her damage is insane for all the CC in her kit. She's like Xin Zhao release OP. Mark my words and watch for the nerf stick to come quickly. GG.

I go:

Berserker Greaves (Attack speed = more W bonus damage)
Trinity Force
Warmog's
Bloodthirster
Black Cleaver
Guardian Angel

Works like a charm.

Really don't see the benefit of Tri Force on Vi???? Its way expensive and you can just get Phage to FroMal which is a better choice. She only has 1 ability that scales on AP and the ratios are crazy low. Don't waste time and money on Tri Force...

That's my opinion...

Mov spd, attspd, sheen proc, mana, hp, ad, slow proc.

The thing is that it is super cost effective, and works really good on her she has low cd AA enhancer, a 3 hit proc on w that benefits from attspd, shield based on total hp, her weakness is kiting tf gives her a mov spd boost+ a slow, tf+boots of swiftness+slow mastery.

Her kit works like Irelia and Jax, AA enhancer+dash+short CC and survivability

Edit: btw, you guys need to stop building her just tanky, keep in mind she is getting her values nerfed.

And you cant build her on the same steps that irelia and jax, i usually get a phage then a brutalizer(viceversa depending on who am i agaisnt and whos the enemy jungler) after phage and brutalizer i get sheen or zeal(again depends) then i finish tf or get a giants belt for survivability(which i turn into a sunfire cape after triforce, im still undecided on sunfire or randuin but hp and armor works wonder for her passive) and then upgrade brutalizer to black cleaver and then last 2 slots i usually build bulwark and hydra(bulwark more hp, regen, armor, lots of mr and the aura for team and hydra for aoe+lifesteal)

Personally, I like jungling as her, and build as follows.

Ancient Golem
Berskerer Greaves w/Furor Enchant
Iceborn Gauntlet
Black Cleaver
Maw/Mecurial Scimitar (depending if they have burst or lots of CC)
Frozen Mallet.

Attack speed reds and MS quints. She becomes almost impossible to peel and the aura from Gauntlet makes it harder to chase after her when he socks your carry.

I build her like this:

Swiftness Boots
BC
Runic Bulwark
Zephyr
Iceborn Gauntlets
BT for Damage / GA for Defensive

Sometimes I even build manamune on her. When it switches to muramune, the toggle is insane on her.

Black cleaver even worth it for her after the nerf?

I think the BC is still good on her. Her W passive already reduces armor so you don't have to depend on the BC for that. You could skip it and I have at times for a BT and just grab the brutalizer for some CDR and other items for health. I guess it just depends on you, your build and your play style.

I understand TF has a lot of benefits but just saying there are much better items for the cost. TF is a mixed bag of fun but not all the stats truly benefit Vi. Jax has both AP and AD scaling on more than one ability where as Vi only has that AP scaling on her E so the two aren't really comparable. Irelia also has both AD and AP scaling on her E and R so in my opinion the TF isn't the best item. But everybody has their own way of playing and building so no 1 build will be the best. If you like TF, then use it, if not then don't.