Currently, characters have base HP and base stamina. A level one brand new naked alt in the start zone has 22 base stamina, increasing base health by 40, 1.8 health per stamina. Of their total health of 123, 83 is base health. At level 90, same class, same race, base stamina is 164, but that gives 2036 health. This is around 12.4 health per stamina. Level 90 health for a naked restoration shaman is 148,699, so of that, 146,663 is health.
So it's a big drop. Celestalon also comments that HP per stamina will reach 30 at level 100, so the HP from stamina will be higher. But it's happening to everyone, and to everything. Removing base health and relying on stamina has several implications, and is a pretty smart way to go about a health squish.
First up, the basic impact of the removal of base health is that there's a huge drop in numbers. That 146,663 health you just lost? You did nothing to earn it, apart from leveling up. There was no real gameplay, it's just a stagnant number on your character sheet. And now it's gone. You will still have base stamina, which you'll gain with levels, which will offer some measure of base health. Naked dueling? Still a thing!
But all of a sudden this big glut of health is gone. Now every point of stamina on your gear means more. Stamina suddenly becomes a far more meaningful stat. While it was always useful, in Mists, one point of stamina only contributed 0.00008% of your total health. This will have been a contributing factor to stat and gear inflation, as the same thing happened across the board with numbers becoming less and less meaningful. If we still had a big blob of base health, numbers on gear would mean less.
And this has to apply, in my opinion at least, for damage and healing too. Base damage and base healing should go, and everything scales on points on gear. There's no bloated numbers sitting around with little to no gameplay value. Every point of the now-shifting base stats becomes more valuable, gear becomes more significant. It makes it easier for the devs to ensure your gear is a meaningful upgrade without massive inflation.
Update: Celestalon has responded on Twitter to the issue of damage and healing scaling:
@oliviadgrace Re: a question in that article... Yes, base damage/healing on spells is removed too. All from scaling. Equal scaling for all!- Celestalon (@Celestalon) December 2, 2013