I haven't used molasses, but have made several brews with dark sugars, like turbinado, muscovado, jaggery, etc. Usually 1/2 to 1 lb. in a 5 gallon batch. It does add some dimension to the finished beer. Add it at or close to flameout so you don't cook off too much of its flavors.
Only 2oz. molasses in the recipe? They're going conservative with it. But be careful, as too much can take over the flavor. Especially the darker varieties. Start out with the 2oz, and if you can't detect much, use more next time.
