WTF with chat-shown damage?

[Uberling]

Did fight today some mob, die and bother myself to scroll chat window a bit higher and count numbers:
So: Opifex fixer, level 132 at full health (3157 hp) and two HoTs start to fight enforser:
730 melee damage
400 melee damage
Healed 99
Healed 552 (First-Aid kit)
414 melee damage
Healed 195
Healed 141
603 melee damage
Here i got to run few rooms back.
Healed 109
Healed 195
Healed 160
688 melee damage
414 melee damage
873 melee damage
You died of weapon damage.
So what the f*c*? Why i die? There are must be at least 487 more points of damage.
Why not all damage shows in chat window?

[Darkbane]

I've seen this on several occasions. No idea what causes it, but when you end a fight having taken about 500hp according to chat, yet are now on 500hp out of 5000.... and i've seen people die from this too...