The couple of times I've flown AY to DFW in the last 12 months immigration has taken either 1-2 minutes or 45 minutes. The 45 minute wait was when the lines looked absolutely impossible and stretched all the way close to the jet bridges. Still made my 1h30 connection so I would say DFW is one of the better US airports for immigration.

There are also several security check points to choose from after dropping of your luggage. The one closest to the exit from immigration often has the longest lines as that is where the signs direct you.