Ohh my goodness there is soo much wrong with that it is a scientist's nightmare!
Speaking as a scientist who is also a archer I would be happy to point out that a fantasy game is not reality... There are no elves, there are no giant eagles,no goblins and no dragons... Technically it's a scientists dream... However just to clear up the situation a little...
Though realistically speaking the elf likely would have been injured simply dismounting the Giant Eagle going many miles per hour (Id guess around 120 MPH) upside down.
I didn't imagin the elf dismounting the Eagle while it was upside down or while it was moving that fast... But rather just after it grabbed the dwarf after its powerdive... So it would be briefly on (or at least close to) the ground... Kinda Like when you watch real birds of prey catch rabbits... So it starts off soaring on a thermal... Rolls over in the air, is briefly upside down, elf uses this time to pick a few targets and fire off an arrow or two... Eagle completes roll into a dive... Then for a moment after grabbing the dwarf the Eagle is on the ground, or close to it and has changed vector from straight down to up... And the elf hops off during that brief time... Having
somehow avoided whiplash when the Eagle hit the Dwarf.
Though that would be fairly entertaining to watch
It would be fricking awesome
Also I don't know if the Eagle would slice heads off with he talons. I'd think they would be graspers so to speak in that they attack with their claws by grabbing and/or raking
It's a legendary trained War Giant Eagle... With razor sharp steel talon spurs strapped on... I know they're not in game but so what...
Also sorry about bad spelling, formatting and grammar, I'm posting from my phone which is a little tricky. I'll clean up both posts when I get to a computer tomorrow. Also it's 2am here and the first post was made on the bus home from the pub and this second one was made after a short post-pub post-chinese takeaway "nap"...