You'll always want to use /SCH if you're trying to achieve max Damage, Hailstorm, Higher Base INT, etc. If you're doing this in lolAbyssea, don't use Ultimate, just get Hell's Guardian, PW is a joke to kill, Main Atma Set you want is Minikin Monstrosity, Hell's Guardian and Beyond. Don't forget to burn the target (Lowers their INT and makes nukes hit slightly harder). Another option is also the BLM Mythic WS, Vidohunir, which lowers the foes Magic Defense Bonus. And the most overlooked piece in the BLM Arsenal, Spirit Lantern, an additional 10% added to all of your nukes is invaluable, the drop rate isn't as bad as some people insist, I have 5 sitting in my Dbox (You can send them to yourself) and I just pull them out as charges run out.
Other then that, there's not a whole lot you can do if you're solo, unless you can call on some people to give you a SCH's Augmented Hailstorm with AF2++ Shoes, BRD for Etudes x2, COR for MaB Rolls, GEO for MaB+ and Magic Def-, etc.
Now for the gear, below I'll include a gearset, obviously the Bokwus Set is all considering you've taken the Magic Attack Bonus Paths in each piece, resulting in the top of the line set to date. The Waist you'll notice is Maniacus Sash over Elemental Obi, that's because as you stated you want the max damage, the only way to achieve that damage is to reach a lucky weather proc while wearing the top damage Obi.
ItemSet 304897