Saw some guy with 800 wins that was absolutely awful last week . I gave him the benefit of assuming he was just a really bad troll but soon discovered otherwise. He was legitimately trying to justify not taking Eidolons as Enigma and after seeing a couple minutes of his other games realized he wasn't trolling. This isn't an isolated incident and he is far from the worst I have ever seen. Been seeing a lot of players"main" heroes for about 100 games in a row, and never play others, which almost automatically makes them terrible a large amount of the time.
On topic: Probably about 300 hours play time you start to see a real difference. It also hurts your learning drastically when you play with very bad players, and it happens often.
So many edits, argh it's hard getting used to this new keyboard.
I've played about 14 hours, and i still can't get the hang of it.
Are there some heroes that i should completely avoid, because their either very hard, or just bad?
How soon it takes you to get better is all dependent on you. It varies from person to person. How many hours/games you play is irrelevant, it's all about how fast you pick up on things. How much time that takes depends on how much effort you're willing to put into the game.
There is a good chunk of heroes that are hard to play for beginners but that doesn't mean you avoid them. That's why bot games exist. Try to test out every hero over the course of time. Who knows, you might actually be comfortable/good with heroes that most would avoid due to w/e.