As of patch 3.3, the fireballs launched from Captain Skyshatter are glitched, and instead of dismounting you, they're only stunning you for a second
This achievement is still very frustrating to do even after 80, mainly because you don't get access to 310% mounts in Netherwing Ledge (the Dragonmaw Netherdrake is set up to 280% if you enter the ledge with a 310%) and one dismount from the fireballs = gameover, possibly leading to death.
With the glitch, you simply get a really short stun and makes the race a breeze.
I have video proof of myself running Skyshattered and finishing it on the first try, but I got dragged into an Uld 10 group (XT is the weekly) so the video will have to wait for a while.
EDIT: Video is now up! It might be still processing as of 3:35PM EST.
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I didn't cover anything from the video since I trust the community. If you post my character's name anywhere within MMOwned, I won't refrain from reporting you.