Exclusive weapon types are nothing new. In fact, rogues have one... we're the only class that uses agility daggers. Hunters are the only ones that use ranged weapons. Both are technically equippable by other classes, but no one else actually wants them.
It would be nice if Rogues are able to use glaives in future expansions just because they look so cool. That's assuming they actually drop; DHs can use other weapons, so glaives might just never/rarely show up on loot tables similar to spell fist weapons and 2Hs. Agi 1H swords are fairly rare too, because enh shamans can't use them.