The one issue is that most heroics are tough later on and really require you to form a proper group that follows the mmo trifecta. Auto grouping would not give you the proper group builds. It worked in WAR because the areas basically created a large sized group with it's content meant to be done solo, where you need the group to take on boss level characters and it was really a competition to seewho can do best in that quest area. Heroics in TOR are set up more like traditional quests that simply require a proper group usually to do.
Yup, you can't put out enough damage with 4 dps if there's a boss mob at the end of the heroic quest. For example in the h4 daily on Belsavis, the boss hits for 2-3k and a dps would have a hp pool of 13-14k. He has about 160k hp.
You can however duo it if either you or your buddy is heal specced. That is, if you can pass the trash leading up to him.