1. There's more to being a good Jedi than combat ability.
Indeed, but the OP is talking about strictly martial skills. Sparring can only take you so far, because the rest is dependent on combat experience, where theory doesn't always apply.
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.
I can agree with this, but we really lack a frame of reference. I mean sure, Mace Windu was one of the best duelists of his time, but how would he stand against a staple of the Old Republic era like Darth Malgus (himself very skilled with a lightsaber) or the Hero of Tython?