(Referring to current PBE changes changing all crit items to give 25%)
1. Tryndamere Exists, and having a 10% chance to not crit is much more forgiving than a 15% chance to not crit, which reduces chances of frustration when you dont crit for ~3 times when Tryndamere attempts to kill someone or something. It will still happen, but at least Riot can say they tried to prevent it.
2. Having 105% crit chance does not feel like that much of a waste of stats. It would still make things feel smooth, unlike previously when having two zeal items with IE gave you 20% crit over the limit.
3. It is unlikely that Tryndamere will get a buff that makes his passive crit scale with levels or something to 40/45/50% crit
4. This change won't buff Yasuo :)
5. Tryn will be much weaker with Phantom Dancer being less useful for melee bruisers who want it as well as the Conqueror removal, and so pushing back a little power to hit shouldn't hurt much unless Tryn is already considered too broken and unhealthy for the game in lower elos, which I doubt from personal experience. Who knows though, he might be one of the top 5 most unhealthy champions in lower MMRs.
Interesting Facts: Spellcheck thinks that the word 'Tryndamere' is supposed to be 'Daydreamer'. Never knew this before :p
PS: I am aware of the fact that these changes are meant to tune down the overall damage of crit users and to reward having more crit items, which means that any added power for quality of life for one champion irrelevant to the pro scene may affect the bottom lane power balance by quite a bit. However if that happens we can always just reduce scaling ad or health scaling for crit adcs.