Elementalist should have medium HP and Mesmers the lowest for cloth wears. I have never understood why Mesmer had medium HP as of the cloth wearers they are the most "rogue" like. It would take what? A few lines of code to do? A simple fix to help a underperforming class and one that is a bit "overtuned".
Before the "haterade" starts, I have 19 level 80's, 2 of each class (3 Thieves), and truth be told of the classes I have bothered to kit fully ascended one of them is Mesmer.
Honestly, on a skilled Mesmer it would probably not change much save adding a slight bit more excitement for the "danger" factor. There still plenty of tools left in the bag for survival. And an added bonus, when folks complain about Mesmer you can now say "Dude, Mesmer's have one of the lowest HP in the game". However, the HP boost on an Ele would be greatly appreciated, especially for my kind of builds that tend to be more in your face.