Definitely. Also, the individual rounds could offer lower exp, while the boss offers a very significantly higher amount of exp. I know that when doing Zombie Queen II for maximum experience, I seem to get 240K experience for each round, and there's 3 rounds. Instead of taking advantage of that by just doing rounds 1 and 2 and skipping the boss, I'd prefer getting something like 80K experience for the easy 2 rounds, and a few million experience for killing the boss (which when doing solo takes about 5-10 minutes).