I'm not sure if I agree with this, I really love having Eos use souped up Whispering Dawn + Fey Union during big pulls in dungeons, as it's essentially a good 10+ seconds of hands off time during which I get to DPS without having to worry about the tank's health, Whispering Dawn costing gauge or forcing me to use either or doesn't sound great.
The problem is that Fey Union, while amazing in dungeons, is nigh useless in raid/trial environment where tanks keep swapping/taking damage at the same time, and where the whole group is taking damage.
