OK, I played around with DarkStarStorm's bair combo on heavies a bit, and these are my findings.
Firstly, you can't reliably use this in neutral. The timing on bair in order to wavedash out of it means that it needs to be done early, so the only real way to do it is to RAR bair. Any other option requires you face away from your opponent, and doing so means you lose fair, nair (in most cases), dtilt, jab and ftilt as viable options. Keeping options open is good. Also, because it needs to be done early, if your opponent shields, you get punished. Hard. This means you need to use it in a situation where you are in advantage, so we are already out of neutral. Alternatively, you can use it as a mix up I guess, but you loose too much movement options for my liking. If you're using it in advantage, I think that generally there are better options (shffl double fair -> whatever you want for example).
Second, with the f-throw to Fsmash. This works well on heavies because they are so damn big. I don't have too much experience using it against heavies, but I know that it can be DI'd out of. I know for a fact that my friend's Ike can DI out at about 5%, but he's not heavy anymore, so that's a little moot.
In all, I think that if you have the chance to do this combo, then generally you have the chance to do more (since generally you will be punishing a miss or something, and heavies tend to have a lot of endlag). Also, and this is just my playstyle, I'm not a fan of approaching with RAR or even shffl in neutral. If they see it coming, you're dead. If you have them in slight disadvantage it can work, but for neutral, keep working on that movement and baiting.
I didn't really test if the combo was a true combo or not, I'll have to get on that. But that requires me to look at percentage ranges, and I have work now.
Edit: Forgot to mention that in the case where you dash dance away and they follow you this might be useful, but I'm not sure if its as useful as (say) turnaround dtilt or even turnaround/RAR fair.