There are two difficulties to choose from for WoW TD 2: normal and hardcore. You can play the game cooperatively or by yourself. When you first enter the game, you choose the difficulty and what your tower builder is going to be. They range from a basic energy builder with no benefits up to an ArchAngel that can attack enemies as well as build units.
Most of the "towers" in the game are WoW-related units. Night Elf Archers, Orc Warriors, Goblin rogues are a few of your choices. The Night Elves are females that even have their bouncy idle animation.
When the game begins, a path is made which often loops back upon itself and leads up to your ship which is in the center of the map and is the main thing you are protecting. The mobs will follow this path until they reach the center. Each wave of monsters consists of ever-increasingly powerful World of Warcraft creatures starting from boars and moving all the way up to Deathwing.
WoW TD 2 is a fun, simple tower defense game, but it's not very pretty, the instructions are obviously from someone for whom English is not the first language, and the minigames are a bit annoying. When I say it's not very pretty, I mean it is set in a place that looks like old school Desolace and the ship you are protecting is just a small ship in a puddle. But regardless of its drawbacks, it is a pleasant diversion for a handful of playthroughs.