I don't think there is enough evidence to right off Herrera in that position yet. He's had half a douzan games there and never with the same team / set up around him. He's good on the ball, he's tenacious, he's committed and as much as it pretty irrelevant he's a bright lad that speaks well.
We won 4 titles out of 5 and reached 3 champions league finals with Carrick and Scholesy. Pogba and Herrera for me have the potential to be every bit as good and successful pairing.
I don't really want to see us with a DM, destroyer, ball winner because all of those players are limited. Herrera and Pogba can be press, can both break up play, can both get stuck in. I can accept that on occasion, they might not track a run but so what, that happens. I have seen opposition midfielders run off Keano and score goals. It happens, get over it and accept it. The major criticism with Moyes and LVG was their obsession with the opposition. Lets make them worry about us a bit more and (with in reason) play as many good footballers as we can.
For a couple of seasons when we have had a bunch of fannies playing for us I can accept the heigh / presence argument. But i'll say it again, with Smalling, Pogba, Bailly and Zlatan we don't need height. Why add more height and sacrifice technical ability, mobility and creativity when it is exactly those 3 things we need more of.