I've noticed the past few games I've been to since our lord protector Sandro got injured, that Dembele seems to be sitting deeper than previously with Parker more advanced. I made this point to the guy behind me yesterday and every time our play broke down it seemed Parker was 10-15 further forward.
This clearly seems the wrong way round a) due to Dembele's ability b) due to Parker's predictability in attack (think he's fantastic....just not good going forward).
With Holtby roaming, I feel AVB should work on not having Parker venture further forward than the centre circle and then push Dembele on a bit.
The 2/3 players he skips past on the half way line, might not be so easy on the edge of their box but it will surely lead to more free kicks in dangerous areas and a few times breaking through and laying it on (like against Man U where Dempsey's shot was saved).
This has definitely been happening, though I do think they switch it up a bit from time to time, tbh I think there is both a benefit to it as well as it's obvious draw back which you above.
Dembele has a lot more physical strength in the centre than Parker, and this was shown on a number of times yesterday when he bossed Cabaye and Perch to win the ball. It's just a matter of finding a balance to allow both of them the time to roam forward / drop back. IMO.