Party/Character optimisation in Golden Sun

So I have jumped back into a nostalgia trip recently, starting with Golden Sun, then I'll be moving on to Golden Sun 2.

When I played originally, my adolescent brain was very much "stick to the rules", and I would avoid mixing up the classes as much as possible, only switching djinn to allow for Psynergy like "Growth" on a strictly necessary basis, and setting djinn so that they wouldn't affect the class if I didn't have enough to keep the party mono-elemental.

However, I have been dabbling more recently after watching some speedruns and playthroughs, looking into mixing up the classes a bit more. I found this page which goes into the breakdowns and requirements for the "best classes" for each member, and so far I have made Isaac a "Ninja" class, and Garett a "dragoon" class. However, while I am finding the classes more enjoyable for their diversity, damage output and utility, I've had a few issues with stats.

For example, the Ninja Class has one of the best DPS Psynergies I've seen so far (Shuriken), which deals the same damage to all targets hit. The problem is that it drains PP like no tomorrow.

So what I want to try is this:

• Isaac: Ninja
• Garett: Dragoon
• Ivan/Mia: White Mage/Hermit (haven't decided who will be which yet)

To keep things simple: which stat(s) should I prioritize for each character, abased on the class I assign to them?