FG is not the reason to nerf a card, though, so a buff back would be nice. But according to creature cost mechanics, FFQ is just balanced.
Firefly Queen 7 = 3 attack +4 (Spawns creatures) +2 (HP > 5) -1 (duo ability) -1 (Air Bonus)
Quoted directly from the wiki.
So, a buff or not?
That is a bit out of date (it was first generation).
1) The Elemental bonuses have been fully discredited since the Gnome / Dragonfly buff. Now the cost of drawing a card (+1 cost unit) is included in the left side.
2) Firefly is a Duo card, using a Third element to generate a Duo card is usually a Trio ability (-2).
Firefly Queen 6
+ 1 card = 3 attack +4 (Spawns Firefly) +2 (HP > 5) -2 (trio ability)
However this is from the 2nd generation when a 3rd generation theory is overdue.