We were almost all there once, yeah. My first playthrough used Vivian very heavily because Fiery Jinx is really really good out of the box. Actually, Fiery Jinx is still really good no matter what because it's the first access to full-screen AoE you get, and it's not too expensive for the cost. The only downside it has is that some enemies are immune to fire.
Nowadays, though, I understand how to pick up the Mega Rush P in chapter 1, buy Quick Change ASAP, and by level 4 or 5 I have a badge setup going that has a partner with +5 attack much of the time. Once you can buy Point Swaps in chapter 3, they start to work as a nice way to refill your FP while setting a partner to 1 HP easily.
Even without the fiddlyness of Mega Rush P, just putting on the Power Plus P badge from chapter 3 eventually becomes pretty feasible even if it's expensive, although it's better for Goombella than lot of the time since it's +2 to her damage while it's +1 for everyone else's basic attack. Yoshi will still hit for a minimum of 1 per hit if the first hit does at least 1 damage, though, and if you get up to big attack numbers (e.g. Power Lift + other boosts stacked) then eventually every point of attack is +6 damage for him. A +20 attack Yoshi hits Bonetail (2 defense) for 99 damage, for example, although you can do all sorts of nutty stuff like that if you allow badge stealing or game corner badges.
I wish the game was difficult enough to need any of this. I think you can beat the game dropping every point into HP. I know as a dumb kid thats how I beat paper Mario 64