Chain Lightning and meteor swarm have inconistent line of site checks
Chain Lightning, Meteor Swarm, and possibly other area effect spells have line of site checks that are more strict/not consistent with direct spells and ranged (archery, throwing) attacks.
You'll often get "Target cannot be seen" while targeting monsters at the edges of the water in the tokuno snow/ice area, whereas using a direct spell there is no problem, nor is there a problem with arrows hitting those (often static) targets.
It's possible the area effect spells are calculating line of site on all nearby mobs. That shouldn't cause a failure, at worst, the mobs with no LOS should simply not be hit.
Expected result: the area effect spells should not outright fail. Feel free to remove the nearby mob line of site checks, to save some server CPU cycles, if this is the case.
Broadsword, feel free to PM me or reply here if you need more repro details.