Shade has no buffs at all besides MW30, but it's one of the highest DPS/best bossers ingame, so classes aren't judged by their buffs. NW has passives too and high damage and they're pretty fast, and very OP hypers.
They just have higher natural damage while other classes may have lower base damage that gets improved with buffs. Said buffs are always on anyway so it doesn't make a difference.
It's just basic game balancing and really doesn't mean anything.
Lol, so what's booster? +2 att speed = 15-20% more damage. What's Shadow Partner? 70% more damage, twice as many lines. There's more to having damage than +40 att. Those set boosts are actually among the weakest of the damage boosters.
Just because they have no damage boosting buffs doesn't mean they have no stat boosts at all. Throwing Expert adds 30 attack and Dark Blessing adds 30 attack and 15% ignore. Then they have pretty good damage %'s on skills, fast attack speed, a pretty strong DoT, and bats which add another layer of damage and mob control as well as giving healing.... Buffs aren't everything