Ryujin
Legend
IMO, this discussion should have ended a long time ago.
Its not a gray area, its not RAW vs RAI or anything else. Its not even ambiguous. Unless stated, a power needs LoE from its origin square (in this case the caster) to the target. And means all targets, whether of the attack or of the effect.
And I definitely agree, though I think that the issue here is the rule statement regarding teleportation, itself. I think that some people are hanging their hats on the fact that teleportation requires line of sight, but not line of effect to the destination. They are also quibbling that the "target" isn't the character being teleported, but rather the target of the original attack. As you and I appear to agree you still require line of effect to the character that you want to teleport, as you are trying to effect that character with a generic power.
I might let the player do what is described here if the purple worm was transparent, because that would be in keeping with the concept of requiring only line of sight for teleport, but even that doesn't exist here.