As seen here: http://www.reddit.com/r/Guildwars2/comments/2hs8tf/does_fall_damage_seem_absurdly_sensitive_to/ I am hardly alone in this issue.
I’ve randomly dropped dead walking down stairs, I’ve gone splat after jumping off a ledge as tall as my character, yet I’ve lost maybe 10% health jumping off a ledge four times as high.
The general consensus seems to be that either;
A) Fall damage has no internal cooldown, even something like a 500ms delay would stop people dropping dead when they run down stairs or slopes.
B) Fall damage is calculated using how far you’ve descended in a certain amount of time.
In that thread someone posted a link and a time stamp of a guy’s livestream, where he was clear of enemies, ran down some stairs, and literally just dropped dead after his health drained. HOW DARE WE HAVE THE NERVE TO USE A SPEED BOON DOWN A SLOPE OR STAIRS.