Although I'd much rather hear it's my fault than realizing Hearthstone is badly designed game :D

It's not that Hearthstone is a badly designed game. Just Arena is a mess currently. Team 5 had actually fixed this problem at one point by dramatically increasing the incidence of spells (spells often allow you to swing back into the game - having an extra card means you're more likely to draw into removal etc) but streamers whined that it made decks of the same class feel too samey (too many Flamestrikes etc), so they nerfed the shit out of spell incidence. They also broke buckets, another working feature, for a similar reason (buckets created decks that were more similar to each other).

It's too bad, all the "Arena-only" streamers who played Arena simply for the increased variety / decreased consistency of experience (more "entertaining" content for Twitch) have abandoned Arena, so it's kind of a trash can designed to cater to players who have moved onto other game modes.