Guild Wars 2

I main a ranger and have recently picked up the 1500 range longbow trait to try it out. One thing I have noticed is that the harpies in this fractal almost always (70-80%) become invulnerable when I attack outside of 1200 range. I’ve also read that enemies will become invulnerable if they are unable to attack you. This seems self-defeating…

I picked up the trait line to specifically attack enemies from farther away and because these enemies do not move from their platforms they cannot attack me (with their regular attacks) when I am outside of 1200 range. I now cannot attack them because the game states they should be invulnerable if they cannot attack me. FUTHERMORE if I close distance, even to mele range, invulnerable often STILL affects my attacks.

I do not understand why this is so in the uncategorized fractal when, in for instance the solid ocean fractal, this has never once happened when I attack from max range.
I would think that extending the range of a weapon by +300 would mean we are supposed to be able to attack out to 1500 range in normal play.