So the PHB seems clear with Line of Effect on 1 target at a time: if you can pick a corner and draw a line to any of your target's corners, it's a valid target. But what about when you're targeting multiple people with the same power? For example:
So in this example, its clear by choosing the "northeast" corner of his square, our player can have line of effect on the kobold on the north side of the wall but not the south, and if he chooses the "southeast" corner, he can target the south kobold but not the north. So, if he uses a power that has multiple targets, can he hit both with the same power at the same time? Is that answer different if it's a close burst power? Logically it would seem since each square is 5x5, unless someone was 25 square feet large, the power would originate from the same corner for all targets; if you're in the northeast corner targeting the north kobold, you can't simultaneously be in the southeast corner targeting the south kobold. But obviously logic isn't always the best benchmark for these types of things. If anyone has a non-ambiguous cited answer I'd appreciate it!