Guild Wars 2

I have had this happen again and again – I am fighting a mob with a larger health pool, everything is going fine, until suddenly the mob turns invulnerable, regenerates to full health and then attacks me again (and I usually die). I know this can happen when you pull a mob too far, but these were all cases where I stayed nearly on the same spot. It is incredibly frustrating.

I’ve had the same exact problem, mostly in underwater areas or with really large monsters, it may be some strange location detection bug. I know mobs can do the whole “I’m invincible and regenerating my health” thing under two conditions;
A: Too far from their spawn
B: They cannot fight against their opponent for whatever reason. (They can’t get to you and as such are invulnerable’d)

But in all the recent incidents of monsters going “Haha you can’t kill me” neither of those have been the case and it concerns me as I’ve died more than once because of it (other mobs agroing or it being a veteran mob) Mobs that behave in this manor also seem to have any timers they have refreshed such as skill usage/minion summoning.