Mirror Coat reflects all Special-category moves, while Counter reflects all Physical-category moves.
Dark Pulse is a special move, so yes it will be reflected by Mirror Coat. Serebii must have it the wrong way round - special dark types would be immune to Counter, and physical ghost types immune to Mirror Coat. It's not really important though because Wobbuffet would have both moves.
Also, Tyranitar is a physical pokemon so you should be using Crunch on it instead of Dark Pulse anyway! If you come across Wobbuffet you're best off Swords Dancing until you can get a 1 hit KO.