Description: At the area, Thil Mountains there is an Earth Genasi spawn that appears between the destroyed Tower, and the Undead Resting Place, on a ledge further down. If one engages said Fire giants, the earth genasi lock on to you and come chasing across the entire map to get out on your way out. We went into the Undead Resting Place when we first saw it happen, but on our way out the same incident repeated itself.
One of the fire giant spawns in question is bugged as well, in that they are fenced in as they spawn. What happens is that the sorcerors start spamming spells that reach without even being near you. Perhaps this is how the earth genasi lock on to us without line of sight.
We tried to leave but as we neared exit of the map, the earth genasi were upon us, taking us by surprising, ending in full party wipe.
As per what Dorg said, I am also fairly certain that the Bioware perception part of the AI is working like designed.
As for the design of the spawns, that's a different question, and though it has been a while since I actually messed with the giants up there, I do recall something funky about how they spawned behind the gate, though it didn't dawn on me at the time that there might be a problem (perhaps because we survived the last time I was there?). The spawn could probably use a tweak so the giants don't actually get stuck, because while the spell spamming is annoying for the PCs, a bunch of giants clustered nice and close together is also easy pickings with AOE spells used by PCs against the giants.
I know the Earth Genasi have certain perceptive abilities and are placed in that part of the map for a reason (by design, though that design is not to trek across the map to chase PCs heard fighting on another mountainside), and I'm not sure if there is anywhere else that makes sense to place them, or any way you could change their spawn to make it so that they don't trek around the map and surprise attack PCs at the cave transition (which is rather mean, because you can't see them coming at all, and they aren't really supposed to be in that part of the map).
Perhaps raising the platform upon which the giants spawn by one more level would give enough space so as not to kick up the genasi.
*coughs* well my comments about the gensai were more along the lines of Milt's observations about possibly relocating the gensai or raising the platform to avoid them from chasing PC's, not so much about it being a bug. Understood that if its an intended "ambush", then by all means let them rage. Although, I do recall certain spawns in Sharawood being moved to avoid an ambush type scenario near an AT transition.