I somewhat agree. Yes, the AoE damage is lackluster. But it can be useful against groups. Any more damage and there's too much overlap with other skills. And it's a mobile AoE. PG, MV, HoB all have inductions or channels.
It may not be the best Ammo : Damage ratio, but it has uses. Aside from great sound and animation, I use ER for the knockback combos (as you mention). Throw a Sticky on a forward target, ER to knock him back into his buddies, boom! Likewise, for knocking enemies off cliffs, watch the hilarity ensue.