Hajek didnt struggle in Hartford. He's the type to do better at higher levels. Usually flashy players have a harder time transitioning because they face tougher opposition, but players who do small things well do better at higher levels because those plays get ruined by the crappy minor leaguers anyway.
For ex, you go into the corner and under pressure from 2 opponents quickly flip the puck to where your teammate should be. Great play if your teammate is an NHLer who understands where he should go to receive your pick, but when your teammate is 3 days away from the ECHL, your flip pass is probably going into empty space or your teammate gets there late and turns over the puck or Gilmour grabs the puck and tries to pretend he's Leetch, only to badly turnover the puck on his own blue line, so you saving the puck in the corner doesnt matter because the other team wound up with it within 4 seconds anyway.
Players like that usually do better at higher levels, while players who can abuse children in the Juniors because of a size advantage or because they can out-skill someone who will be working as a junior car mechanic in 2 years, those prospects get all the hype before landing in the ECHL.