You seem to be forgetting Yoda's words" "Wars not make one great".
1. There's more to being a good Jedi than combat ability.
2. Wars can make for improved techniques, but it seems they don't necessarily.
3. There were revered duelists in that era. They stood out as few probably because of the sheer amount of Jedi.
All excellent points, however, I never disagreed with Yoda's philosophy or your first point there. Jedi are not all about combat, and I think that Yoda's statement is an excellent insight into the mindset of the Jedi. They do not revere war, and unlike the Sith, do not hold combat skills in as high regard as they do other areas of expertise.
Kreia's statement is certainly a controversial one, and interpreted many ways. However, I think she was speaking more to the exceptional dueling abilities of the Sith Lords entombed on Korriban, as compared to current combatants. I include her statement only to counter the inevitable "newer Jedi/Sith are exponentially better than the older ones!" that seems to get brought up all the time. I like to interpret it as meaning that combat skills ebb and flow, and after the First Jedi Purge combat knowledge with lightsabers was dwindling, whereas during the days of Marka Ragnos and co. it flourished.