Dark Mind will reduce Royal Fount by just as much if you don't delay it for Dark Wall instead. If you use Dark Wall a few seconds after the first adds die you mitigate 30% of heavy damage(>12k ignoring autos) directed at you during an AoE phase that will save your solo healer a major headache.(Gunnery Podx2 + Royal Fount + Auto-attacks) You still get to use it again on the second Plasma. You're just seeing roughly 3k more damage on one tank-buster to make an AoE phase mid DPS check easier. Either will work fine, I just wanted to point out this method because I consider it better.