In my oppinion: True damage is way over the top in this game! >_>

wow, i'm happy that yi is able to do his job for once

That's a lot. But he's also nearly full build while you only have 2828 health. At 33 minutes your build is rather minimal, so I can't be sure what happened there, but typically to deal that much true damage with Wuju style alone (not smite) Yi would need to bash on you for a few seconds. Being that the power disparity between you two is so large though, that probably only took about two seconds. (Your log says 2.81 seconds, which is about right.)

I do think Master Yi is too linear, and a touch too strong because of it, but in the end he's not usually ruining my games, and in order to deal that much damage, he's forced to build almost purely offensively. The new champ can deal 1000 or so true damage on her Q as well if built correctly, as can Cho'gath. (Albeit, on his ult.) So this isn't unique.

I'm not sure if it's unbalanced or unfair though. I haven't had many problems with it in the past. (Excepting on Vayne.)

As a tank though, it's no fun to deal with.

Nope it's fine, one of the few remaining sources of threat for a tank and their degenerate builds.

enemy vel koz did 1700 true damage to me yesterday in 3 seconds

Trundle pillar does 1 true damage. Op

I mean, I can't really make a solid call off what I see in the screenshot. I imagine if he smacked you around a lot, yeah that sounds reasonable, he has the items for it, but the amount of time it took is what concerns me....

True damage is fine for the most part. For Yi in particular, his true damage is justified by him being a melee carry who needs to have comparatively higher dps than ranged counterparts and who needs to be significantly more effective against tanks since being in melee range makes a tank's job easy. This same logic applies to Fiora and GP's true damage as well, and for GP and Yasuo's free armor pen.