Undoubtedly, the best way to approach Abyssea is with a few friends. If you take a party in there, pimp them out with Atma and Abyssite you can tackle damn near anything successfully. Add in that you're friends, and the give-take sort of lotting let's people get pieces finished without being greedy dicks or ninja lotting asshats.
I'm happy to report that I finished off the Abyssea zone Mega Bosses and all the
Time for bed!