Faerie Dragons and Nimble Escape

[Paul Farquhar]

Abilities don't work in isolation, it's how they combine that determines how challenging a monster is. If a faerie dragon had 3d6 sneak attack, then an ability that granted them automatic advantage on attacks would significantly increase their damage output. But as it is, they try to annoy players to death with illusion spells and insipid cuteness, so Superior Invisibility is of little offensive significance. It just makes them slightly harder for angry players to stamp on.

Ergo, DMG has rough guidelines for estimating challenge ratings, not hard and fast rules.

 

[Yunru]

Abilities don't work in isolation, it's how they combine that determines how challenging a monster is. If a faerie dragon had 3d6 sneak attack, then an ability that granted them automatic advantage on attacks would significantly increase their damage output. But as it is, they try to annoy players to death with illusion spells and insipid cuteness, so Superior Invisibility is of little offensive significance. It just makes them slightly harder for angry players to stamp on.

Ergo, DMG has rough guidelines for estimating challenge ratings, not hard and fast rules.

Except the DMG has rough guidelines for estimating how any given ability (from the small list at least) affects any given monster. And it's wrong.
What's more your argument doesn't even make sense, Nimble Escape and Superior Invisibility both offer the same offensive advantage, regardless of how much effect that advantage has.

 

[Paul Farquhar]

The DMG rules are based around the idea of damage per round. Since a faerie dragon has a DPR of (roughly) zero, gaining advantage on attacks does not affect their damage per round. Zero times anything is still zero.