Now that you point it out, I do admit it - Konan proved so much an obstacle to Obito that he had to use an Izanagi on her. And her death was just plain sad - not so much for how she actually died but just how much potential was wasted - like I'd have loved to see her fight with Sasori in the Creation of the Akatsuki, or any other fights. Shippuden did a bad job with promoting characters.
Again, we must not forget the fact that she probably knew a lot more about Obito's techniques than, say, a kunoichi from Konoha at the time. Plus, there could well have been a Plan B ready with the Amegakure Orphans just in case Obito betrayed them - after all, would you trust a random masked guy who comes up to you out of nowhere for a partnership? Nagato's decision after Pain's defeat, and Konan trying to prevent Obito from getting Nagato's Rinnegan all suggest that she could have been preparing to face off against Obito.
Frankly, we can't judge much from a single fight. I mean, to compare the Konan that lost graciously against Obito with any other kunoichi is difficult, perhaps even inconceivable. But the fact that she wouldn't have gotten far with fighting Jiraiya means she isn't the strongest out there. I would rate her at 3 or 3.5 out of 5, but again, because of just 1 complete fight, its wrong.
There are several kunoichi who could significantly harm Konan, and probably not as much who'd be able to defeat Obito. Sakura (4th Great War), or like you said, the older kunoichi like Mei or Tsunade, could have easily overcome Konan.