100th win, 200th Ranked game this season. Qual'd for another series.
By the end of laning phase, bottom was missing both lane turrets, top outer was down, and we had yet to take a single turret. We did, however, take the first dragon.

Cait had about half of Trist's CS through all of laning and beyond, mostly from getting constantly bubbled by Nami and having to b from Tristana's subsequent harass. (Yes, our Cait was getting harassed by Tristana). I managed to keep both opponents low enough that Xin could come gank and kill them, and that was about the only thing saving the lane from complete and utter failure. After laning phase the entire team went nuts warding and clearing vision in our own jungle, catching Darius/J4 a few times in the process. Each catch had us recover a little more, push up a little more, until eventually we had a near-Ace and pushed up mid with Heimer, Cait, myself, and Shen still alive. Took their inner, base, and inhib in mid, then top inner, then Dragon. And from there fought on even footing, started outscaling the enemy team hard (I very nearly had a completed Void Staff while keeping up with Oracles.

In the aftermath, a few things caught my eye that resulted in their team throwing such an amazing early lead:
1. Darius and J4 both primarily build Armor, when the primary damage threat was AP coming from Heimer and eventually myself.
2. Bruiser Fizz, while damned near impossible to catch/kill, didn't contribute nearly as much as AP would have (being able to instagib either myself or Heimerdinger). They didn't need a bruiser, they had Darius and J4. They needed that assassin.
3. Between Heimer's turrets and my plants, we had so much persistent AP damage that J4 completely melted every time he ulted someone. Darius started dying a lot more towards the end as well, usually from being away from his team and getting caught out alone. His build wasn't exactly spectacular either.

Basically, in the end game they were entirely reliant on Tristana for their damage and she just couldn't do what she needed to do. My team came together and made smart decisions, theirs split apart and threw. Very hard fought match but a rewarding win.

Xerath started with 2 FC and some potions, while I went for Dring+pots. This became a chalice vs 2x Doran Rings. Both of us consistently went nearly OOM trying to push the other, but I usually came out ahead in cs and health. I can't really fault any of his itemization, considering how far behind he ended up being in gold/cs. Dunno how I feel about Zhonya's on him, though - he may be the one mage I wouldn't buy it on given his ridiculous ranges. If someone gets to you, you're probably dead anyway. I'm still debating whether it was right to delay my Zhonya's, but I think it paid off in the end. Most fights the enemy were nowhere near me (half of them I had to flash in to snare/ult because I was so far back) so I rarely would've needed the active. I traded up the Doran's for a Grail after finishing Liandry's, once I had mid pretty solidly won.

Vayne's build was solid (excepting perhaps Trinity, now that it's post-nerf for Ranged?). The GA was a bit early, but she didn't have the backup she needed to fight through our ridiculous AOE and cc, so it's understandable. Ultimately she just never got going past laning phase and stayed basically useless. She might've had a bit too much attack speed/mobility and not enough damage assuming Blood Boil was on her constantly. Not sure about the Corki Cleaver and Cowl (Half his skills do magic damage and he already has plenty of true damage/armor shred, half our team was heavy magic damage. He probably could've used something else more effectively, but at least it has AD, CDR, and HP). KZ also had one, so it wasn't really necessary on Corki. Cowl is weird when only Xerath has magic damage, but it did help him recover HP through pre-fight poke wars.

Sona and Nunu: Pretty standard support builds. Sona was basically correct in not finishing Locket given that Xerath was so far behind for most of the game, but the active would've helped a bit in a few situations. Given how much she was wandering around alone (No idea how she never got caught out alone when she was in the river where we had no vision. Nunu never got boots2, but Blood Boil makes that not as bad. He didn't ever really do anything besides bloodboil Vayne and blow up anyway.

KZ/GP: I have no idea how Kha Zix didn't finish his Muramana. I think he bought the tear late, at which point why bother. GP basically went critplank/pokeplank and did his job well enough - a few ults from long range caused issues in early teamfights before the damage started falling off. He was pretty successful split pushing/keeping KZ top lane but became massively useless when we started getting ahead. He still contributed a lot of damage, but the bar is misleading - most of it was chip damage/pre-fight poke that quickly got healed away. GP was the only one on their team to get Merc Treads.

Lee / J4: I love J4's Randuin's Omen, great buy vs a Vayne. Gives you a ton of defensive stats and cripples her mobility if she's trying to fight you. It won't stop her from killing you, but it makes her take quite a bit longer to do so. I don't recall seeing him use the active, but most of the teamfights had spell effects everywhere, so hard to say. Lee bought a sunfire but never splitpushed, so I can't really say that I think it was a smart buy. The Ninja Tabi on Lee were a horrible choice: Corki does a lot of true damage and damage through skillshots anyway, KZ has plenty of non-auto attack damage...Merc Treads, CDR boots, or Mobility would've been smarter. Not sure about hexdrinker on J4 either, given that basically only Xerath or GP are likely to trigger it.