When you have 400 Armour and as maokai and cant last more than 5 seconds against the enemy yi....
It was scary.
It was scary.
Were you just Armor and no health? That may be the reason
That's called diminishing returns. Once you build 200-250 armor, the additional armor you buy will provide MUCH less protection. After that point you should build offensive/bruiser items or MR.
5 seconds is super fucking long lmao wtf..
When fighting a Yi you also have to damage him. Someone like Garen would have won that fight because he can kill the Yi in that 5 second window.
Build thornmail and Yi is zero problem for any decent Maokai.
Vi's job is to blow up tanks by reducing their armor with her abilities, doing % damage with her passive punching tank buster ability, and the fact that most VI's tend to build a lot of pen (from my experience and guides and such). It's no surprise because that really is her job, though she shouldn't be getting 5 seconds in a team fight like that with all the CC so it is unlikely this will happen unless you are out of position when playing against a vi in a similar circumstance or something.
When it comes to Yi which is who you said you had a problem with, that's because Yi does A LOT OF damage, but is really easy to HARD CC and shut down (He is squishy). Just get thornmail, and stick with your team instead of trying to 1v1 yi. Yi does true damage with his ability (sort of mimicking tank-bustery stuff like vi?), but he doesn't do as good as a job considering how squishy he has to build, whereas vi can build bruiser or full tank and still be plenty effective.
Maybe, just maybe, it's because Yi has on-hit true damage combined with 2.0 Attack speed?
Stop crying about Yi, he is supposed to be one of the strongest duelists in the game. And splitpushing is impossible in the current meta, so he is relegated to 1v1's (which rarely ever happen) and clean-up duty. He's trash tier.
Don't use your damage reduction, knock-back or root or anything.
Because then he might die in 2 seconds instead of you letting him auto you to death. This sounds less like a balance issue and more like a positional issue (yours). If you were near your team and they had 5 whole seconds to watch him auto YOU of all people, perhaps it would have gone differently.
did you try pressing any of maokai's buttons? they usually help