So I've been maining Vi for awhile now and I've come to the realization that her late game leaves a lot to be desired. Her early game bursts are monstrous and I've gone 9/10 games dominating my lane, then winning ganks. After that though in the teamfight phase it seems there isn't much Vi can do without throwing herself in the middle of the enemy group. Her Q and R are both suicide if not done correctly and you can't land her E without getting up there either.

What do you guys think, and what are your suggestions?

Just get decently farmed and ULT and do your thing on the ADC or AP carry lol, Vi is so good at taking down those poor squishies with no GAs ;A;
Anyways, you can get couple of defensive items if you're worried about survivability but otherwise it shouldn't be a problem since most of the time the AP or ADC will be in the back and the strong melees will be in the front handling ur other strong melees.

I do try and backdoor do that whenever possible. Nidalee and Sona are some of my favorite targets. Once the team wises up though and sticks to a more dense formation I find I still run in to the same problems though.

I've seen a lot of success peeling for my Ad's and stuff unless you have a super good initiation comp and then she should just dive in.

I think if you play Vi as a split pusher or assassin rather than a bruiser, you'll see her shine better.

Her 1v1 power is very, very good. She also has good wave clearing power. That makes her an excellent choice for split pushing. And if you set her to the task of dunking the enemy carry in a teamfight, she'll do that easily with the appropriate damage items.

Remember, it's ok to trade yourself for the enemy carry in a fight. Especially if you can take them out quickly.

Her knock up is extremely powerful, and she has amazing peeling potential. Obviously if you go in first without amazing tankiness you're gonna die and be useless, but if you stay back and peel, you'll actually be pretty helpful

If anything late game is where Vi shines. A full build Vi is monstrous. Don't build her for damage because her W takes care of that. Build her with tons of HP and grab something to increase attack speed (Wit's End or Trinity Force).

Personally I roll these full builds.

Jungle: Berserker's Greaves, Spirit of the Ancient Golem, Frozen Mallet, Randuin's Omen/Black Cleaver, Banshee's Veil, Guardian Angel

Top: Ninja Tabi/Mercury's Treads, Frozen Mallet, Randuin's Omen, Wit's End, Warmog's Armor/Black Cleaver, Guardian Angel

Tons of survivability (especially with her passive) and lots of damage output regardless because of her W. Obviously items are situational -- if you're snowballing top things like Black Cleaver and Trinity Force are recommended for pure damage output.

mmmm

So I tried out prioritizing attack speed and HP and I am really enjoying the results. Won 4/4 games with Vi in the jungle and I can say I'm quite a bit more confident initiating team fights and not dying!