Ran'jit doesn't have a "power level" supplied by his dragon. No one has power levels, this is not Dragonball Z. Ran'jit has a wealth of both combat experience and life experience in general. The dragon familiar is an accessory, one of many advantages he's picked up over a lifetime of experience; it's not the sole reason he was able to overcome us. He knows tricks that we don't, which is quite reasonable as our own characters still have plenty to learn. Even disregarding the special advantages we had in those fights, the ability to defeat a Primal or a Dragon or even a fully-realized Ascian does not automatically translate to ability to defeat someone with a different skill set than they have.
Who says Ran'jit couldn't kill a Lightwarden? He probably could. Ask Titania what happens when you do. And Minfilia wouldn't be any help there - she does not do the Light absorption thing that we do. She was with us for most of our Lightwarden kills, and she didn't do any absorption there, either. If she had, it would have saved an awful lot of drama later on when we became overburdened.
Any advantages the Echo gives us in combat are fan speculation only. This is deliberate, as the game writers don't want to trample on the narrative players make for their own characters' backgrounds. A lot of people would resent the implication that we're only strong because Hydaelyn made us strong. Because of this the only confirmed abilities it gives us are passive ones - the ability to understand languages, the ability to see the past in peoples' memories, resistance to Tempering. Fordola's Resonance-enhanced fighting ability tests this, but in the end it's still not expressed in-game that we're better fighters because the Echo makes us so. (And a good thing, too, given how easily Fordola's "advantage" was overcome. Good thing our combat skills can't be shut off like her's can!)
For all their longevity, the Ascians are not skilled fighters. They are manipulators, and the only times we've seen them engage in combat are with us. They've probably done so at other times in the past, but in twelve thousand years, I'd guess the amount of actual combat experience they have with individuals whom they can't simply snuff out with a flick of the wrist likely amounts to less than even ours, let alone Ran'jit's. Before they became Ascians, they were scientists, philosophers, and intellectuals, not warriors. The Ancients were a peaceful people, from what we've seen, living very harmoniously with one another. After becoming Ascians, they encourage people to kill each other, and rarely have to do so themselves.
We've only scratched the surface of of Ran'jit's history, and it's clear he was an important person on the first. He's not no one or nothing - he's basically Batman in terms of reaching the heights of which a human is capable. We, too, are at those heights, as is Zenos. And there will doubtless be other peak humans we'll cross swords with in the future. Expect other mortals to be capable of testing our limits in the future - the game would be pretty lame, otherwise.