The "Hybrid Tax" is a term used to describe the baked-in reduction of the DPS of classes that can fulfill multiple roles. There is not necessarily a limiting factor that is visible in-game, nor is it a drastic reduction, and may be partially overcome with high skill. However, in general a class that can fulfill multiple roles will naturally have a lower DPS than "pure" DPS classes (IconSmall Hunter Hunter, IconSmall Mage Mage, IconSmall Rogue Rogue, and IconSmall Warlock Warlock). This hybrid tax is merely in place to maintain the popularity of pure DPS classes, since there would be a drop in their popularity if hybrid classes could produce the same DPS while having the advantage of taking on other roles as well. Again, it is not a steadfast rule or reduction but the tax is generally present and the reason why most averagely skilled hybrid DPS cannot outperform a pure DPS class in its element.