Well in the Power of the Jedi Sourcebook (under his character section) it said that nobody in the temple had ever seen him hold a lightsaber indicating that he didn't spar with any of the other Jedi, at least at the time that the statement was in reference to (though the databank does credit him with a victory over Mace Windu, so if we accept it as a canon statement we have to assume that they may have sparred afterwards).
In Jedi: Mace Windu, during the Clone Wars has began, a Jedi asks him if he wished to spar and Yoda responds by saying his practise with Dooku was sufficient, in reference to a battle that occured months earlier, indicating that even in the war, up to that point in time, he still didn't spar with the other Jedi.
In Yoda: Dark Rendezvous, within the first chapter, it's stated that as Grandmaster of the Order, he rarely left the Temple, and we know that when he did participate in the war, it was largely as a Jedi General and not directly in the combat, where even when it was, he would have also had access to his Force Powers, and would have been using his lightsaber against enemies that function compeltely differently to opponent swordsmen.
Essentially, his experience against swordsmen type opponent was in all likelihood limited to his duels with Dooku during the war, and a very limited number of sparring matches against the other Jedi, and his general war experience, which wouldn't have call upon practise with the weapon against sword wielding enemies, would have been very limited, both in comparison to the other Jedi as well as in comparison to the time he spent in the temple or as a general.
Ultimately I'm lead to believe that his technique by RotS wouldn't have been great, especially next to Kas'im's phenomenal ability, and I don't even know if I'd say he was that powerful either. Throwing debris around and moving at flashy speeds is good by a certain standard and clearly what the films are trying to show you were exceptional at the time, but I think even there Kas'im outperforms him in his defence against Bane's Force Wave and ability to keep up with him in combat.