There are See Invis mobs everywhere, since LU 12.
Orginally there were supposed to be a lot of mobs that could see though invis. However, there was a bug that caused mobs to spawn without all their inate abilities. If a mob was aggroed and reset it would regain them, but since folks could invis in by, or would kill 'em, the usually wern't around.
Anyway, it's a tough neighborhood.
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