Bergvall and Sarr are both better at progressing the ball. Palhinha and Bentancur aren't of a standard that you need the likes of Modric or Kroos to improve on them. They're both at best average footballers with Palhinha being excellent at breaking up play but nothing else.
None of our midfielders are good enough to play in a 2 together - we will get over run by any team with something about them in the middle of the pitch.