I can confirm this too. My main (Level 95 Hunter) was trying to browse the warsteed cosmetic sets (since I believe the Marauder set is currently on sale) and I get the same error - that there is nothing available for my character. This despite the fact that I've never purchased any of the "basic" warsteed cosmetic bundles from the last expansion - they don't appear as available either.
[CENTER][color=yellow]BRAITHIR[/color] - Elf Hunter (Explorer/Tailor) * [color=yellow]GLAMWYN[/color] - Man Champion (Armsman/Weaponsmith) * [color=yellow]GORBODOC[/color] - Hobbit Minstrel (Yeoman/Cook)
[color=yellow]GRIMHAF[/color] - Dwarf Guardian (Armourer/Metalsmith) * [color=yellow]MORDENUS[/color] - Man Captain (Historian/Scholar) * [color=yellow]SABELTAN[/color] - Man Burglar (Tinker/Jeweller)[/CENTER]