So in order to have more compelling gameplay you want other players to get hurt more and risk the healers not being able to heal them fast enough? You want the tank and dps to be able to die faster so that your gameplay can get better? I do admit they could make some dungeons a bit harder in that aspect but not all of them. What you are asking for requires a lot of balance and may end up upsetting the dps and tank community more than you know, which I think may be the actual goal here. I am sorry if it isn't but now it sounds like a troll post. "Make the game harder so I can have more fun." From a business perspective it would likely hurt the game more than help it. You appease one group and upset 2 others because you are asking them to take more damage so you can have more fun. It sounds to me like you might just need a break from healing. I don't mean any of this in a bad way but what you are asking is for 2 other groups to possibly not have as much fun so you can have more.
Now tanks healing themselves... that is another story all together. I admit it is a little too powerful for a couple of classes and needs to be toned down a bit but there are other things that come into play. For one, in the time I have been playing (which has been since commercial release of A Realm Reborn), I have only ever seen it in 4 man regular dungeons and very low level. As far as taking over healing for an entire group... maybe 1 or 2 heals but not for a long period. If they can do it more than that then yes there is something wrong there that needs to be looked into but you make it sound like they can keep an entire 8 man group healed for a long period.