I finally got around to buying Yi, and it turns out that was enough for me to remember that I'm a complete asshole. Because I build him with 100% crit chance. Don't get me wrong, I've seen very clearly the ways in which an organized team can shut him down, but I've yet to see anyone try it.
Basically, I use the same build order every time. I'm in the jungle, so I do the bog-standard machete+pots start, but from there it's: Hydra, Mobis, Phantom Dancer, IE, Youmuu's, and a second PD to finish. I originally tried zerkers but with the full build there's already a stupid amount of AS there. Basically, full build means that: Every Q crits against all four targets; every AA is a 250% crit; I have a passive +100% AS from items alone before Highlander/Youmuu's active; with the auto-crit and AoE damage on my AAs from Hydra I have stupid amounts of lifesteal; between Highlander, Youmuu's, Ghost, mobis, and the extra 10% movespeed from the PDs, I am stupidly slippery.
The 25/7/14 stuff surprised me when I was testing it. The easy multikills were funny. The retarded-fast pushing and structure killing was great. But what really sold me on it was soloing Baron in around fifteen seconds and coming out with full health. I just lost it for a minute or two at that point; my team was posturing mid and told me to start Baron for us to bait them with, so I went up to it, and by the time they started heading my way I had finished it. xD