My raid was trying to figure out how on occasion the Shield Generators in the Firebrand and Stormcaller fight are being destroyed prematurely. The shields take the damage from Firebrand's Mortar Volley effect and will eventually fall as a result, but sometimes the shield drops a little early resulting in players taking direct mortar volley hits. We were also certain that none of our DPS was using any type of AOE nor were we targeting the Shield Generator directly.
I looked through my combat log and I noticed a few things:
1. It doesn't look like the Mortar Volley can crit.
2. The damage shows up in my combat log as being MY damage, not the boss's. I'm guessing that each player being hit by the attack contributes the same amount of damage (would need to have logs from other members of my raid to confirm).
3. Because the damage is credited to me, it is occasionally triggering my proc relic (I currently use the campaign version of the energy proc). The effect shows as "Lightning Spike" in the logs.
This is from our kill last night: http://www.torparse.com/a/16621
00:36:08.599 Quorra's Lightning Spike hits Shield Generator for 209 energy damage, causing 156 threat.
00:36:08.599 Quorra's Mortar Volley hits Shield Generator for 169 damage, causing 126 threat.
The amount of damage I did to the shield with mortar volley is rather small, which makes me think it doesn't have much health to begin with (would be nice to verify how much HP the shield has in HM). As you can see the proc from my relic is actually doing more damage to the shield than mortar volley is. So we might want to consider changing out relics before this fight to make it go smoother and lower the risk of player death from mortar volley direct hits.
Granted, the proc relic didn't cause much damage in the case of my parse (only three hits total), but I expect that this would be more significant depending on how many of your DPS use proc relics and how many players you put under each shield. But it is a peculiar result nonetheless.