My suggestion is simple. The elevator pitch:
It would both be incredible and be hilarious if the only way to respec is an option to have 1 respec or loot drop and it is only from the final boss of the game.
After the boss is defeated on a realm, the respec has a chance to drop again from any loot table, but at a very rare rate.
This would keep respecs rare, earned, but more importantly a Player must bear the curse of the Rime of the Ancient Mariner… wandering the isles for eternity, warning all about shooting the Albatross.