I think it's more for mana starved Agi heroes who get an early ring as their sole mana sustain (like brood, for example).
WR is flexible enough with her itemization that she doesn't need yet ANOTHER regen item.
I don't care.
And doing some mathcrafting:
Two Wraith Bands (970 gold):
6 Damage
12 Agility
6 Strength
6 Intelligence
Ring of Aquila (985 gold):
9 Damage
6 Agility
3 Strength
3 Intelligence
1 Armor
2 Armor aura
0.65 Mana Regen aura
Wraith Bands are the offensive choice and Ring is the defensive choice. I could certainly see getting the ring on Viper/Razor using Wraith Bands on Drow/Sniper.