Ok this isn't as crazy as everyone is making it out to be. I mean Death Knights basically have some self healing talents to take care of themselves. So the concept in theory is sound. However, I think the main difference here is that you are kind of basing the success of this build off of healing meters in low end dungeons and raids. Also you are sort of ignoring the fact that you could probably just equip better gear and use better talents to get more mitigation, and then when threat isn't a problem swap to seal of light or something. I would highly doubt it though since you'd lose a lot from switching off of seal of vengeance.
Here's my suggestion to put this build to the test. Download skada and instead of using healing use absorbs and heals. This will acount for any overhealing you are doing. Then compare that number after the fight to the healing meters of someone else to see how much overhealing you are doing and what the main spell is that is causing that. JoL is very much a padding spell so you can't use that in this build and say it works. Literally any holy pally could use it and do more healing with it and you would STILL get the healing from it being used and would actually heal more. You are basically using it to pad the numbers and I guess generate some threat for yourself.
My other suggestion is to go into higher level content with the same group of ppl. That might take a while before you can do this. But actually try out RS 25 HC before saying this is viable. If you can't do LK or Halion then the build already isn't viable. And if you r healers say that you are easier to heal with a more conventional build then the build isn't viable. No sense in constantly putting you healers on edge trying to heal you only if they then start struggling to heal the raid also.
Those would be my suggestions before spending more time with arguing with people.
