I'll just jump on the bandwagon and join my fellow shadow priests in the protest against this change.
For me Improved Vampiric Embrace is one of the most Iconic attributes of the Shadow tree, the capability to be a caster who can take a good beating and regenerate health through damage done is what made me choose to play and enjoy the shadow priest more than any other caster class hands down.
In PvP, imp. Vampiric Embrace is close to absolutely essential if you are going to survive any 1v1 brawl against a decent opponent, without this small but important healing buffer, we will become an easy target to wiggle down in a 1v1 scenario, and no, larger healthpools will only delay the inevitable as aside from Dispersion we are lacking in the defensive cooldown area.
I know that I could've just posted this in one of the other topics on the matter, but fact is this attracts more attention from the occasional blizzard gooneys that you can bet lurk around these forums too, gathering impressions and feedback on the changes from the community.
Let shadow priests keep Improved Vampiric Embrace Blizzard, it's a key attribute and iconic to the spec itself!