Misread the "they wont part". Thats my bad. But beyond that, the exclusivity thing I think is still a non argument. It's a pointless 'exclusive' if all you had to do was show up and read some quest dialogue.
But I think thats a wierd way to look at it? SE gives you the option to purchase items from past events...so thats a bad thing? I mean compared to WoW (or atleast how it was - been a few years), you missed an event its tough shish kabobs. Kinda makes newer players or even veterans who missed it cause real life be left out. Beyond that, theyve been pretty consistent on exclusivity. You cant get variants to ultimates unless you do it, as an example. It seems their position is exclusiveness sits in the realm of challenging content.
The Online Store outfit is the seasonal event one, not an actual dungeon set, though it's probably most similar to the Striking set.
If they make a dyeable version of the dungeon outfit, it'll be in a future dungeon/raid or crafting recipe (hopefully the former for me).
If the Mog Station version does indeed mean we'll never get a dyeable version in-game, I hope we at least get dyeable versions of the flower headpieces. It's disappointing that they weren't included in the Faire set to begin with.
As a counterpoint to "they'd never make them dyeable in-game because nobody would buy the Faire version", I think there are a few reasons why they could happily coexist.
One is model variations. If people don't want sleeves on their healer top, or they want the skirt on their caster instead of the bikini bottoms, they need the Faire version.
The other is level. You can equip the Faire set at level 1 and as soon as you start the game, but if they put a dyeable version up in a level 80+ dungeon somewhere, you're not getting hold of it for ages and you still can't use it as low-level glamour.
Saddly, dyeability is considered a very special thing in this game, instead of a normal/common feature so... probably won't happen