The State of Top Lane: AKA Nerfed Midlane
Dear, Riot
This is ridiculous, at the end of last season you guys told us the fighter reworks were coming, you mentioned darius and garen, we saw kits for yorick, jayce, and rengar, and you basically told us that you understand fighters don't have clearly defined roles, and you were working on it. But since the beginning of preseason the only rework to come out is the rengar one, which was supposed to push him more towards fighter, but didn't really. he's still way better as an assassin. The only other changes fighters have gotten since then is nerfs:
You nerfed fighter itemization. Randuins and Wardens mail; self-explanatory. Dorans; terrible on most meeles now. BotRK; i'd argue the slow is more important on meeles. Sunfire; straight nerf on a melee exclusive item. Spirit Visage; Almost exclusively used on Melees. Frozen Heart; buff and nerf but the AS slow was important against ADCs.
You buffed ADCs ability to kite. See the youmuus, and mercurial in 4.10, and heal a while ago, although it was tuned down slightly.
Any fighter that was strong was nerfed. Jax, Renekton, Riven, Nasus, Shyvanna, Shen, and even Wukong, Olaf and Lee sin, although the first two are because of jungle, and Lane-sin nerf was just minion shielding.
The only Buffs have been the recent J4, Malphite, and Rumble, which were small but a nice start, The Nidalee and Rengar reworks, bruiser Nid is strong, but Rengar is still an assassin, and a super minor darius buff.
That being said, Let's look at this weeks LCS picks for Top Lane, or as I've been calling it Nerfed Mid Lane, because apparently it's now where mid lane champions go after they have been nerfed and are no longer good enough for mid lane. The picks were almost entirely Kayle, LuLu, Gragas (3 nerfed midlaners), Jax (who got nerfed in 4.11), Renekton (because he can lane against anything), and a little bit of Shyvanna and Irelia. I'm not saying LCS is the be all end all, but pros are picking what they pick for a reason, because it's the safest thing with the highest impact on the game. Mages shouldn't be the safest default pick in top lane. This is the culmination of the way riot has handled fighters over the season, fighters as a class are on a downward spiral and I don't see it turning around anytime soon.
EDIT: I'm not saying that the nerfed champions weren't too strong, but that doesn't change the fact that the constant nerfs are a contributing factor to the state of fighters as a whole.
TL;DR: Riot said fighter reworks were coming, instead they've nerfed every strong fighter, nerfed fighter itemization, and made it easier for ADCs to kite them. As a result the default top lane picks have become mid laners that aren't good enough to go mid anymore.