Regarding the idea of splitting the draw between 3 buttons: The Offensive button, the Defensive button, and the Resource button, the Offensive button will be chosen most of the time for sure. That said, if you still have Divination in place, or a form of additional DPS gain that requires the additional seals, then both your Defensive button and your Resource button are contributing to rDPS. The difference here is that, in the duration of divination's Cooldown, you're looking for the moments where the Defensive and Resource buttons are best useful so that you have Divination ready to go when it comes off cool down. You could just burn them for the sake of burning them, the that's what the novice AST would do. The skilled AST would try and find the moments when they are most helpful in the 120 second time frame.

Because of that cool down, you're looking at most situations being 2 Solar seal cards, 1 Lunar seal, and 1 Celestial seal, because you'll need to use each the Defensive and Resource buttons once per 120 seconds. The major difference is choice. You are the one that gets to choose when the non-DPS utility cards are most useful, not RNG.