I'm not really familiar with the d20 system either, apart from limited exposure in the bastardized version that KOTOR I and II used. Yet, I didn't take "30 minutes" to fight and defeat Kreia, or have the slightest bit of problem with Sion.
I'm sorry, but if he had problems with those two, I shudder to think how he'd do in some of the endboss battles in games like BG especially, but even games like NWN, IWD, FO or PS:T.