An interesting thread has popped up on the official Age of Conan forums that alludes to the possibility of new fatalities being earned through instance drops and the alternate advancement system.
Lidsman on the official AoC forums:
That is correct OP, you gain new fatalities throu AA combos/spells and the combos/spells that drops from instance bosses.
Certainly sounds interesting, but we can't confirm this either way at the moment. We'll definitely be looking to find out!
If you've got evidence confirming this, feel free to post it below or send us an e-mail!