Thog has two levels of fighter. He thinks anyone who takes a third level in it is an idiot. (In their first fight, Roy pointed out that he missed out on Weapon Specialization. After being hit, Thog decided to switch places with Nale.)
Roy beat Thog the first time around, so I don't see why there should be a lot of tension this fight. Come to think of it, the OotS beat the Linear Guild too easily. If it's Nale's complexity addiction causing him to lose, fine, but IMO, each side should be able to match the other. (While there's PC vs NPC imbalance on an individual level, Leeky Windstaff was more powerful than any individual OotS member, and Drizzt-backward seems to be beating Varsuuvius handily.)