I came to Multiboxing after single boxing prot warrior, priest (heal and dps), rogue and hunter. After playing that lot all to 70 and raiding with them all I dont' have a problem with understanding a group dynamic. If I hadnt, a mixed multi box group especially with a warrior as the tank would confuse the hell out of me.

What youre doing is playing and understanding the class roles. if you dont get them then its going to end in fail for a good amount of time until you begin to understand whats going on. First off get Omen2 threat meter and put it on each of your guys. With the set up you have to get the max threat from your pally, mana conservative but effective healing and max dps from your guys you would have to be an absolute master of each of those classes and have a very peculiar brain. Clever nmacro management would be essential. Most Multiboxers I have found go for group synergy on mixed classes. That means that their dps and healers although mixed fight well together as they can share macros. A hunter is a very peculiar dps beast imop and when you mix in a lok and then a dps warrior youre asking for trouble.

If youre new to mixed classes i would mix it up just a little bit at first.

Even with having played a lot of classes to and past 70 If i used your set up I would fail very hard indeed. I prbably wouldnt lose aggro but the dps warrior would freak me out. I would use your usual set up but put one new class in then build up from there.