Basically the role of a tough tackling DM has now started to expire. Even Mourinho at RM is using Khedira and Alonso as dual ball distributors but has taken Lass out. The tough tackling ability can be provided by Pepe should the need arise. Even Coentrao our super utility player does not play as a destroyer when used as a DM.
And Busquets is the first name that would get into his spot in a World XI as far as I am concerned. Coming from a RM fan, that carries a lot of weight.
As long as Spain and Barca remain the premier international and club teams that role of the DM will remain very relevant, since having such a player in the opposition mid-field to disrupt the passing game of those mid-fields will be key to defeating them.