At the end of the game you can have everyone with 4 things on status and element-def-j, which makes it easy to be immune or have high resist to all status effects, and you can be absorbing 80-100% of all elemental dmg.

Next you have whatever you want on str and hp since theyre easy to max out with +60% from your junctioned support abilities. Put haste (I think thats the best one) on speed or junction auto-haste.

While leveling just have a "bonus" junctioned for every stat possible so you have incredibly high base stats before even worrying about junctioning.

With all this I had Rinoa with 230+ in str, vit, mag, and spr + auto-haste. She was only the 2nd best in my party, but I guess 2nd's good enough with Squall there. I pretty much was was easy mode once I used Mighty Guard with Quistis (used Zell on my other playthrough but that just wasnt fair lol) since in this game it gives haste, aura, shell, and protect (wtf op).