It won't be exact, but the testing done by many people, as well as myself pretty much shows how you factor Attack Power in to your build equations.

Certain weapons have certain caps, and then you pump Attack Power when you hit those caps. Garuda's Beak is the new 350/310 cap. Basically, it's better to use Ifrit's Harpoon until you have Garuda's Beak and don't worry about hitting 350/310 ^^

Also, yes; Base Damage has the greatest influence on Auto-Attacks, Jumps, and technically Dragonfire Dive since it isn't a "Weapon Skill". DPS is what you use to judge stat caps for that weapon, as well as WS damage overall.