My tactics for facing Jerec are
(1) Try to stay between him and the column. This way, he has to get past me to regenerate.
(2) After Jerec's gone up the tower and I stop the statues, the trick becomes keeping him in the regeneration chamber at the tower's top. The only ways Jerec will leave is if you push him out or if he follows you when you leave; if you keep the duel up there, he won't regenerate again.
The hardest duel in the game is Boc the Bouncing Lunatic, IMHO --because he doesn't stand and fight.
"The Beasts know much that we do not." -Ancient Jedi proverb