Some users have reported issues with line of sight on Ice Blocks during the Sindragosa encounter in Icecrown Citadel on the Wrath of the Lich King Classic PTR. Blizzard has offered some clarity around the confusion, explaining that if you are auto attacking from behind the Ice Block, you won't be granted line of sight to avoid mechanics.
You must turn off your auto attack if the Ice Block is close enough to the boss for you to melee, or it will not block LoS.The original intent is to prevent situations where you’d get behind an iceblock in melee but still be able to hit the boss while in safety. As a result, if you are near an ice block and are attacking a creature, the iceblock won’t block LoS.
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