Does enemy fire just deplete my energy? I get things like "critical health warning" and things go a little hazy but apart from my energy bar I cannot see anything to reflect this. Does this mean that if I use up my energy and sprint into a fight that I will be one-shotted painfully?

ty

Not one shotted, but there's little saving you. There is no health bar, it's all about bloody screen now wich will regen.

No more healthbar in this game, only your energy-bar for your suit-powers.
Which is kinda funny as in Crysis 1, we HAD a healthbar. But Crytek probably saw it as unrealistic to have a healthbar in a game, where your health regenerates after time and you're as good as dead after a few hits (unless you're in armor-mode), anyway.
(Then again, we fight SQUID-Aliens with a talking suit, which can turn us invisible... so much for realism as argument. :/)

Stop speaking as if you got any understanding about gamedesign at all. Regerative health does indeed fit very well with this game.