Randomizing abilities isn't challenging. All that means is if the boss randomly choose to use his good skills consecutively you auto-lose, and if he decides to use his weak skills more often you get an easy win. Due to the fact that skills interact in interesting ways, even if you say Titan must use every skill exactly once before repeating, having a sequence like Bomb -> WotL -> MB is much harder to deal with than Bomb -> Landslide -> WotL, and I'm sure there are easier combination of abilities than what Titan currently does too with the same criteria.