Im not sure Id go that far!
Wanyama is a brick wall, and surprisingly not a bad footballer as well, but Id never see him as offering anything like Dembele on more than an occasional (once in a blue moon) basis.
Dier is much more of a 'footballer' and even he wouldnt really do it either.
The only way Id put them two together would be as @Ade's folks are ok really pointed and we needed an ultra hard to beat set up.
Or, possibly, if we elect to play a total lightweight in front of them.
the season before Wanyama arrived we really struggled in the games Dembele missed, ppg was way down and we really struggle through the centre of the pitch - this wasn't the case last season whenever Dembele was out and without checking im inclined to think there was little to no change in our ppg in the games Dembele missed (due to the teams overall performance i wouldn't be surprised if it was actually up) that to me is down to Wanyama providing more able cover of what Dembele provides to our game - he is strong on the ball and able to hold off opposition players whilst bringing the ball forward.