Looking at your example final build for tank Vi, I would much rather have Trinity Force over Titanic, especially when you already have Sterak's. She's in the top 25% for base AD (#32, and the next 20 ahead of her are less than 10ad@18 ahead of her), making TF a VERY efficient item on her, especially when paired with Sterak's. She benefits a lot from the attack speed since she has %hp dmg every 3 hits. TF pairs really well with Cleaver on Vi, again due to the %hp dmg, though the two items do cap your cdr, and tank items in general have a lot of cdr, which would be wasted stats, granted 10% cdr is only valued at ~248g, so it's not a major loss. Granted I do see the value in Titanic with it's auto reset allowing to proc her W faster, and it would be fantastic with proccing Press the Attack if you went that route. If I wasnt abusing the Sterak's/TF combo, and running Titanic, I would probably just make Maw my MR item and not run Sterak's, as 3/4 of her skills scale on Bonus AD, so base AD is mediocre on her if you arent using it to amp Trinity Force.

I could even seen argument for a late Gargoyle Stoneplate for your MR, as you can pop the active while waiting for cooldown's to come back. Titanic is often built on a lot of top champs to help with wave clear for faster pushing, which Vi doesn't need. She has great wave clear at fairly early levels, especially if you go Sunfire Cape, which is the best armor item after they reverted it back to it's old #'s.

Have you thought of going a different route with Keystone? Electrocute seems wasted when half of her items are tank items. It's not bad early game for lane dominance with a TF rush, but loses a TON of value later in the game when you havent stacked much damage. Press the Attack would seem overall better. She procs it very easily with her auto reset, and it works well with her %hp damage, esp combined with Cleaver. Or even going something like Aftershock, which is currently incredibly strong. She procs that easily enough with Q. Combined with her passive shield, the bonus tank stats are insanely efficient, and the damage proc makes for solid trades. If you go TF, Sterak's, Black Cleaver, you've built up a really good amount of bonus hp, which makes the armor/mr from Aftershock incredibly efficient without having defensive stats built.

It kinda seems like you made the glass cannon version first, then just added a section that basically says, "Or you can build tank items with the same runes". Which technically you can, but you lose a LOT of value doing that. Trading the fast burst of the AD Lethality build means longer overall trades/fights for her, which makes other Keystones far better options, especially when you under utilize the scaling on Electrocute.