If you do not plan on doing the postgame content, or just want to rush the postgame; break Kimahri into the end of Yuna's grid for Holy, he can and will solo the entire game until you start breaking into the creature arena superbosses and dark aeons, but still very well can.

Tidus and Wakka only get particular value out of being multi-hit with their overdrives; which is something that will not benefit you over Kimahri and Auron's overdrives until your party hits the damage cap (unless you are not pushing your party to damage cap for a challenge run or something); other than that you will not see use for them outside of underwater sections, and Rikku is your best friend if you learn her busted (albeit sometimes grindy) overdrive system

I 100%ed on PS3 Version (my first playthrough which was done without guides for the most part) with what was practically a solo Kimahri Carry until postgame then it was Kimahri and Yuna until everything else was done and I had to grind with everyone

If you get Kimahri to learn Holy early on (what I realized I could do) he will break and sweep the game until you hit postgame; where I practically had him solo the creature creations bosses with Yuna on Revive duty until the Dark Aeons and Penance. If you break his damage cap he will be hitting in the 50,000s before any other party member in the game can, and if you rush Nova (the strongest attack in the game until the party hits the broken damage cap, and the strongest attack in the game in the theoretical scenario where you mod the game to remove the damage caps on overdrives) he will easily hit 99,999 with little to no effort; since Nova ignores Magic Defense on top of its high power.

Well...you still gotta use all chara to max out their sphere grid for an achievement. At that point, doesn't matter who you use aside from Yuna so that her Aeon hit for 99,999 every hit

Tidus, Wakka, Yuna from start to finish for me. But then I grind the crap out of that Sin scale fight on the ship for 99 sphere moves XD

@haraxmant I legit did this with Kimahri, and I have him and rikku and yuna doin 9999 before I fought seymour

I use Yuna in post game and it works out fine. It's the other 3 who are useless at that point, especially Lulu.

Lemme comment and say, you've GOT to get rid of Lulu and Auron.
They are 100% slowing you down.

Go Expert Sphere Grid, take Kimahri into an Auron/Tidus Path (for a little STR and a lot of speed), and he eliminates the need for Auron 100%. Since Kimahri also has piercing, and Auron is too slow, hes gone.

And take a small diversion with Yuna into tier 2 magic, and back into her own path again, and suddenly she eliminates Lulu the entire game. Since Yuna starts with a higher MAG stat, and all of her levels make Aeons stronger, Lulu is just a poor choice.

You can make these decisions and changes by the time you finish Luca/Early Mi'ihen, and you'll never need to use them all game!