He couldn't have won back then, though he still almost managed to do so.
Here's why he wouldn't:
1. His Kamui and stamina weren't as good as they are now.
2. Akimichi ruined his plan of taking care of one path that Kakashi said himself he would have taken care of. Because of this that body was not hit hard enough and later interfered against Deva.
3. He didn't have counters to RInnegan techniques (well, he didn't even know what they were at that point)
Right now, Kakashi's mastered Kamui, has decent stamina, knowledge of all Rinnegan techniques and according to what he and Guy said themselves, counters to them... He would certainly defeat the paths he faced back then.
Though he would most likely lose if he was to face 6 of them at once.
He could kamui two of them at the beginning, but doing so rapidly would take a toll on his body, which would make him an easy target for the rest of them. Unless he teleports to kamuiland to rest a little and then comes back, but first of all, I dunno if it doesn't count as forfeiting the fight, and second of all, why would Pain just stand in the same place and wait for him to return?
Oh, and just to make it clear - two paths were enough to take Kakashi down only because the strongest one, who kept up with 6-tailed Naruto all by himself, was one of them.
It's likely that Kakashi would have been able to solo even 4 or 5 of the paths if Deva wasn't among them. I'm not certain of it, but it's a possibility. What I am certain of, however, is that Kakashi would have won if there was any other path instead of Deva he had to fight.