What to do with +Spd -Atk Myrrh?!

Fury+QR is still ok on her.

A while back I looked into a spd-oriented lightning breath build for her for a flier team, and what I came up with I found weird but probably good. Here's how it looks on your IVs:

Myrrh +spd -atk
Lightning breath +spd
Reposition
Moonbow
Fury 3 (or maybe not, because it interferes with QR. Maybe some bond skill or Iote's shield)
QR3
Goad fliers
Iote's shield, or flier formation, or whatever you prefer; you can use QR here and some other B-skill (renewal, maybe, to help keep QR active)

The key here is that she wants to be under the influence of at least one goad fliers. When that happens, her stats are (assuming no A-skill):
47HP, 46/36/36/31
which is like F.Grima with even less atk but significantly more bulk

Bench. -Atk makes her very hard to use. Mine’s +Hp -Atk and she struggles to kill most things, so i killed my f2p Fjorm to give her Atk/Def Bond, and even then she’s still borderline unusable.

Personally, I would keep pulling as many green orbs as possible from the legendary banner until the end of the week and see if I get a Myrrh with better IVs.

I don't normally recommend pulling for better IVs, but there are just so many excellent units on this banner... Not only the new Hector is top tier - possibly even better than Grima - he is also probably the best fodder in the game. (Dist. Counter and Vengefull Fighter in the same unit?) B. Ike is a good unity and excellent fodder, and Myrrh is one of the strongest dragons and the best flyer unit in the game. No matter what you get, it will definitely be useful.

Also, the Myrrh you've just pulled has the ideal boon and bane reversed.