I don't think it was the midfielders who lost their heads, generally (except for Can who definitely did on a few occasions). Plus things like controlling the tempo come with experience and players who have a bit of football intelligence about them (as Hendo and Wijnaldum definitely do, and the young Emre as well) will get better at it the more they play together. Don't forget this was the first season for Hendo at the new position and first for Wijnaldum in this team and they didn't do too badly.
At this point I'm not sure how much difference would buying someone like Paredes make; I doubt it would be much of an improvement, honestly. I would, however, like to buy one more physical CM who can take the ball forward battering ram style and with a lot of energy and desire to fight for the ball. Someone like Bakayoko or possibly Naby Keita, Spurs' Dembele, Franck Kessie. Or perhaps we already have a player like that in Ejaria or Grujic.