So I've seen this brought up several times on why the Illari don't fully heal you. Sorry in advanced but I'm going to bring this up once again. I didn't want to post this in a closed mantis issue or a buried forum thread so I'm making a new one. Anyway, here's my argument for the Illari fully healing you.
First off it just kinda seems like a bug, or at least would be confusing for a new player. I think the Illari don't try to heal you (make the sound an effect) when you are above 100% anymore but it still may be confusing to new players when they pass an Illari while injured and it doesn't heal them.
Second, Chris made the argument that players would warp back to town to heal when they are about to lose a vitality stone level. Can't players already do this though without any vitality stones? I mean if players were going to be this obsessive about not losing a vitality stone level, why would they even use the vitality stones in the first place? The same thing could be accomplished by not using any vitality stones and warping back to town when they are about to die. This is essentially the same thing as warping back to town when you are about to lose a vitality stone level.
A counter point to this could be that the players used the vitality stones because they are headed toward a boss fight and don't want to lose them on the way. But to this I say that isn't really any different than what they can do right now. A player could not use any vitality stones, warp back to town when they are about to die and warp back. Then, once they reach the boss area, warp back to town, use a bunch of vitality stones and then warp back to the boss.
Also, right now I mainly use vitality stones for missions where you can't really warp back to town to heal anyway because that would mean you fail the mission or at least have to start over.
Other place I would really use vitality stones would be in underground caverns, lieutenants and Overlords, but in these cases if I were being 'optimal' I would use the warp back to town before dieing method and just use vitality stone right before fighting a boss.
The only real difference I see between the Illari fully healing you and how it is now is that if a player used a lot of stones before a boss fight and still had several extra hundred percent health left after the fight. Now players can't warp back to town to heal and keep from losing vitality levels between boss fight like they would be able to do if the Illari fully healed them. Maybe this is really a major worry.
Also, right now it kinda seems like you are punishing a majority of players for something a minority of 'optimal' players might do.
Also also, could bosses at least drop health orbs on death?