Normal base payloads for 1/2 ton crew cabs these days are around 1,000-1,500 lbs for a non tow packaged truck, tow package 1/2 tons are generally between 1,500-2,000 lbs, and unique trucks like the F150 HD are between 2,000-2,900 lbs. Of course once you start adding options then these base payloads will drop by a few hundred pounds if not more. My old F150 HD had a base payload of about 2,280 lbs and decked out with all of the options in a Lariat trim left it with about 1,950 lbs on the sticker.
Normal base payloads for crew cab 3/4 tons is between 2,500-3,500 lbs for gas engines and between 2,000-2,600 lbs for diesel 3/4 tons. Again, once you start adding options then this base payload will drop significantly. For example, the base payload for a Ram 2500 CTD crew cab 4x4 is about 2,300 lbs, but once you upgrade to a decked out Laramie package and add things such as Ram boxes, then you are left with about 1,900 lbs on your door sticker.
Both the Titan XD gasser and diesel still fall into the 3/4 ton payload ranges, but on the light side. The only other competitor to them is an F150HD which is what I would rather get instead of the Titan if I was in the market for that kind of truck.