When I first did it, with an Archmage fire, Transdecent fire (me) and Archmage death. It took around 3 hours to complete the whole thing, and the Poseidon fight took less time than the first boss fight (the dang storm sharks!) but I got like three wand drops and no other gear. Are they auto drops? I'm confused on what to do and whether I should get the drops.
My Myth is wearing the Poseidon robe because I liked the way it looks, but she wasn't grinding for it. She just got lucky - it dropped when she was fighting the Sand Squid. (That's a brutal fight - take friends!)
The stats are okay if you don't have Waterworks, but otherwise they're not worth grinding for - if you're gonna grind for stats, you might as well do Waterworks or House of Scales. The way the gear looks is interesting and unique, however - not many people are wearing Poseidon stuff. It might be worth a few tries if looking unique is important to you.
It depends what you want, if you're looking for critical, then go for Atlantea, but if you want damage, use waterworks gear. I recommend waterworks hat and robe because you can't get a really good critical chance until later levels.
So I'd say stick with (if you already have it) Waterworks hat and Robe, maybe Atlantea boots, but I'd say the best crafted boots you can get.
It's not really necessary to farm Atlantea. Most people make do with Waterworks until Tartarus or even Darkmoor although you can get an update at 75 with the Archmage One shot duels.