There are questions about how this pairing will affect the Rockets offense but the way I see it, the duo could be so dominant defensively they more than make up for any loss in offensive output.
Look back at how effective the Taj Gibson/Asik pairing was for the Bulls. They locked down the paint and as a pairing held offenses to less than 90 points per 100 possessions (the worst offense in the league last year averaged 100.2 points per 100). The offense did suffer because neither guy was a threat outside the restricted area but the two years Asik and Taj played together they were +6.1 and +7.2 points per 36 minutes and the Bench Mob often extended the leads they inherited.
Dwight Howard is better than Taj on both ends of the floor and the Rockets are going to have more threats from the perimeter than the Bulls did so I could see the two centers lineup succeed. Probably still a good idea to stagger Asik's and Dwight's minutes so they aren't always on the court together.