I tend to agree. Blizzard should not be looking to reinvent the wheel here for rpg roles. They already have a holy warrior, the monk, so i dont think the paladin is a likely choice for the 5th class. The monk also satisfies fast paced melee class that is lightly armored, so a rogue or assasin class would also have too much crossover.
Perhaps a fusion of the hunter and the druid? A bow user that can also shapeshift and command a single powerful pet?