Why Are Harlequins So Good?

The speed of this style combined with the crazy utility of the Harlequin strats is a ton of fun to play. Transports are so, so useful in a game where you have to survive on objectives. ... It's a potent combination, and your Harlequins hit hard enough to clean out objectives and pick up your opponents major threats.

Are Harlequins overpowered?

Not overpowered. Quite often people who play them have lots of experience with the faction as well as being more skilled than non quin players. "Harlequin players are just better than everyone else" is a bit of a wild take.

Are Harlequins Good Guys 40k?

There are no Good Guys in 40k. Even those with the best intentions have to do evil to make things right. Grey Knights kill innocents in order to hold the tide of evil back one more day.