No, your first thought is exactly what it does. You take the Diablos weapon (which has highest raw and no element as long as you don't equip a Free Element gem), slap Weakness Exploit 3 on to negate the affinity penalty, then Attack Boost 4+ and whatever else you like. Hammer can probably get away with pure damage stuff, while charge blade needs the 6th vial, artillery for max SAED damage, etc. GS loves Maximum Might, that's about all I know about it besides Jagras being best when Diablos doesn't exist (until G-rank I guess).
Since elemental damage is per-hit and does basically the same amount of extra damage whether you're using dual blades or a GS, raw with non-elemental boost stomps the shit out of it when the weapon is super slow.