League is... changed. A lot. In many ways for the worse. The point of many of the powerhouse champions (Garen, Yi, Tryndamere...) was originally to help newer players get accustomed to the game. They were meant to be easy to get pretty good with and make safe picks later on. The problem is, changes to the core game that haven't been counterbalanced by adjustments to these champions have made them extremely powerful now.
If you're having trouble top, I suggest in most cases rushing Executioner's Calling. Everyone will tell you to ignore this item and will call me a heretic for suggesting it, but try it in five games and see if it doesn't help. A lot of top lane powerhouses subsist on healing, be it through lifesteal or ability healing, and Executioner's Calling cuts that down something fierce.
(Also for Darius... A big important note. Unless you have a reliable dash/mini-flash, if Darius pulls you, the worst thing you can do is try to run. Stick to him like glue so his AOE doesn't hit you at the edge, thus healing him and doing more damage to you. Stay there for about two seconds, attacking up close, THEN pull back. Because he's gonna slow you anyway and you're not gonna get away without taking a good bit of damage. Might as well dish it back.)