The mount Terror of the Wastes is supposed to be buyable from Om’sirik upon reaching renown 19 with the K’aresh Trust, but it is nowhere to be found in his inventory (regardless of filter setting to a class or showing all).
Same here. Has disappeared from the vendor once reaching/exceeding renown 19 for all characters on account. Others in guild who are not yet Renown 19 CAN see it however.
That’s interesting. I never saw it on the vendor to begin with, as I looked to see what was next after buying my augment rune at 18 as well as once last week.
Could trigger at 18 perhaps? Or somewhere along the line. I know it was there last week but hadn’t checked recently.
Or maybe it is the buying of augment rune that makes it drop off 
Hopefully our good friends at Blizz can get it sorted.
Looks to be fixed today
And so it is, thanks for the heads up!