Here are theory crafters at work:
6.0.3 Demonology Guide - Page 26 - Warlock - Icy Veins Forums
They suggesting to use cw at 2+ targets. Maybe Millz can change it a little bit or put a trigger as by havoc where we can decide how HoG should be triggered. As example my collegue played several heavy aoe fights with saving HoG to nuke only CWs on the adds and also played ds with cata when adds arrive. This resulted that he out dps´ed me really hard on heavy aoe fights. I know "this is the positive aspect of playing self" but we are here to help improving this cr so it will be a perfect rotation. This includes the DS/Cata improvement which millz will hopefully implement as fast as possible (maybe until ID reset).
Using the CR with cata is a different story then going with 2+ sustained cleave fights. or short burst cleave fights. For instance, lets take a look at Twins. On twins, HOG is better. this is a 2 target fight and having the additional fury from HOG lets you get off more demon bolts. You should not be using CW on this fight even though it has 2 targets, you should be using HOG.
If you are rolling with Cataclysm then the entire process changes. You are less concerned about building up demon fury and more concerned with extremely high burst AOE. If this is your case then yes you should almost always go for chaos wave over HOG.
The middle fight is something like Beastlord. On beastlord you have phases of burst aoe and sustained aoe with the weapons and the wolves. It really depends on what your job is for the boss. With Demonology being so insanely high single target damage, very far beyond anyone else really, it is entirely possible and probable that a demo lock will be put to pure tunnel dmg on the boss ( while maintaining doom on weapons of course ! ) and in this case you will definitely want to roll with demon bolt instead of with cataclysm. To be honest, if your group is at all competent you should NOT be using cataclysm on this fight at least for normal and heroic, maybe mythic but don't know about that yet. So for this fight, with demon bolt and the sustained AOE cleaving that you can do you should really be using HOG above chaos wave for most of this fight. The extra ticks from HOG being on all the beasts + weapons potentially depending on position far outweights the additional damage you would get of chaos wave vs HOG raw dmg. We can debate this all you want and I can do math out that will compete with those theorycrafters, but I really don't see a point. It all really depends on what YOUR role for the fight is, and that changes with every single fight and with every different group. Most of the time I am going to chose single target dmg over aoe. This choice is because my group has 3 boomkins and we don't really need my AOE dmg, but the group really needs my single target, and right now at this point in time, demonology is the 2nd highest single target spec, the top single target spec when a fight includes movement. No one can compete with us single target on a movement fight.
I think it would be best to add in some additional logic to HOG / CW much like you suggested we do, basically a copy of havoc. The option to prefer HOG over Chaos wave or set the amount of targets that each kicks in. If this is at all possible it would be pretty awesome addition to the CR and would handle both your concerns, and my concerns, and allow the user to chose what best suits their role on each fight. For basic users they can just use the default settings and don't have to worry about it.
This is a lot of text but with the importance of HOG / CW in the fact that our entire 4 piece bonus revolves around it, it is a pretty important topic at the moment

All in all, really nice to see some debate going on here

Millz, any input ?