Two players with similar strengths and similar weaknesses that as a combination can manage to slow down any game to a crawl. And one of the partnership is much better than the other...
Lampard and Gerrard were both immensely talented midfielders who played best as a free-roaming midfielder, despite a good workrate. Pogba can be compared to them. Fellaini being compared to them or Pogba is just crazy, really. He is impotent attacking-wise, doesn't have the understanding of the game to play as a holding midfielder and he can't even figure out how to free himself to the pass from the center back. He has the physicality and aggression, that's pretty much it.
The problem with Pogba - Fellaini partnership is that there is only one footballer in this equation.
Pogba isn't well-suited for a midfield two though, that's a given, even with a better player.