It was not meaningless because he is the one who saw through Devas weakness and without that, Naruto would have been captured for sure.
Alone, Kakashi(without infos at the start) managed to outsmart Deva and Asura Path 2times:
- With the raiton kage bunshin. At that moment, Deva was not on his guard. I think he had good chances to kill him at that time if he wanted. Anyway for Asura Path it was almost over at that time since he could get him with the raikiri he had prepared.
- The second time is when he did made a plan with the help of Choza and Choji. There again he could have killed Deva.
That shows that he could have deal with them alone even without infos, so with infos before, he could make a better plan to win this. And don't forget he didn't even used kamui at that time. I don't see what Deva Path or Asura Path could do against that. And if Kakashi needs help he could get support from Gai and Tsunade(better support than Choza and Choji).
With infos, they will know before fighting what is the speciality of which Pain, and will make a good strategy to fight them.
Gai could deal with Gakido, and the one who revives other(who is the weakest Pain).
Tsunade could handle animal Path and the other one who takes souls.
That's why i think the 3of them could beat Pains if they have infos before.
I think you're the one who overestimate Pain or underrate Kakashi, Gai, and Tsunade.