Tryndamere Changes
This is on the level of a micro-rework, and changes some of the biggest problems in his kit in order to give him a healthier spot in the game.
First thing I'd like to say is that I am not suggesting these changes based on whether I think Tryndamere is weak or strong. These changes are purely for the betterment of the game experience as and against Tryndamere.
Most of the time whenever I see any sort of complaint about Trynd, it has nothing to do with "He carries too hard!" or "He is SO OP!" or even "He is just awful.", it is usually "He wins based on luck.". That is a problem. I want to suggest a couple possible changes that could take Tryndamere from being a bottom-of-the-barrel, feast or famine crit grubber, into a respectable melee carry/fighter.
Number 1 change: remove crit from his kit. His passive will instead give him bonus on hit physical damage equal to 0.35% of his total AD per point of fury he has, max 35% AD as on hit damage. The reason this is on hit instead of just increasing his AD by that amount is so that it doesn't totally screw up his crit function if/when he ever buys crit. This is a much more consistent way to give him bonus damage from fury, since instead of a constant toss up of "will he crit me twice and send me to base or get nothing and lose lane hard?" it will lead to balanced gameplay of "his fury is up, so I should avoid his all in and poke him down so he has to heal". This play pattern is similar to what it is now, except that a Trynd who is ahead will not be as likely to throw his lead by not getting crits, and he won't be able to simply get lucky and win off of early level cheese crits either.
To compensate for Crit no longer being a component of his kit naturally, his E, Spinning Slash, will have its cool down reduced by 0.5 seconds per auto attack, instead of 1 second per crit. This will be a slight early game buff, and a slight nerf late, since it is equivalent to having 50% crit chance with the old crit mechanism. This is much more consistent both for the Trynd player and the opponent, since Trynd knows that constant auto-ing gets his spin up faster, and his opponent doesn't have to guess how many more crits he will get.
Number 2 change: give him more fighter attributes. Right now, Trynd plays like a glass cannon melee ADC. There is not anything inherently wrong in that, but I wan't to make a couple changes to his kit that would make room for more fighter-ish builds in addition to his normal ADC builds. First: the heal from Bloodlust will have reduced AP Ratios, but also heal for a % of his BONUS health. This allows for flexibility in his build, where he can strengthen his heal if behind by tanking up instead of just having to build Glass cannon and hope for the best. My other change that could make him more fighter like is to make the slow duration on mocking shout scale off of his total resists (A la Randuin's Omen), having a shorter duration than now at its base amount, but scaling up higher the more resistance he builds. This would allow Trynd to gain potentially massive CC if built tanky, but will reduce the oppressiveness of a full carry Trynd since you will actually be able to run away from him. The removal of crit as a central stat in his kit also pushes him towards a slightly more fighter like play style, so these changes would probably need to be tuned around that fact.
Please comment below if you feel that these changes mess him up more than fix him, and help me figure out how to make him better for the game for everyone's experience!
EDIT: As suggested in the comments, his ult is also a huge problem in his kit, and should be addressed. I am fully aware that it is also an issue, I just haven't had a good idea for a replacement other than some minor tweaks.