Not really underated. I see it as potentially highly useful, but, due to the very limited time afloat (3 seconds?), it's not really going to help you more than burning grenades or two grenades. Sure, it can come in handy, just like any perk, but it doesn't mean that other options are more viable. I REALLY hope a new exptic for warlocks gives AND increases the duration of Angel of Light. I would use it all the time.