If it really works that way (heals reduce rage regeneration), it will probably be due to delay between rage regen and getting hit by something.
So you get hit--->heal to 100%---> no HP lost, no rage regen or you get hit --->no heal or under 100% ---> hp loos, rage reneg.
Personally I wouldn't care as CC would do most of the work anyway, but still worth knowing.
Even if you get healed at the exact same time you take a hit, that's not going to negate any rage generation. Taking any damage, whether it gets healed immediately or not, is going to give you rage. Do you have any evidence to prove to the contrary? The only hits you don't gain rage for are dots, and those that you dodge, absorb, or are immune to. You still gain the same amount of rage for parried hits.
As Raves said, the only relationships between heals and lost of rage that seem logical are the white strikes lost when casting a heal on yourself, or absorbing damage through some sort of bubble ability, as I said before.
On another note, people keep talking about "rage regeneration" but I think we all know rage doesn't "regenerate" or if it does, it's regeneration rate is negative. Call it degeneration, if you will, or just talk about generation rates based on white strikes or taken damage. There is no such thing as "rage regeneration" unless it's negative, regenerating to 0.