It has a very long wind up animation, like the molotov. That's its timer.
So, understanding how the molly is balanced is a great way to explain what is wrong with the rifle grenade.
The Molly's drawbacks actually merrior the benefits of the rifle grenade.
Molly is easy to see coming because of the range; as it's been noted, the enormous range of the rifle grenade makes it difficult to see coming. This is a benefit.
The Molly's locked behind side tech. Costing fuel. Making its appearance inconsistent. The rifle grenade is available almost immediately and consistently used. Molly set back vs rifle grenades benefit.
The Molly's no timer is offset by how long it takes to kill everyone. That is what is balancing it. The rifle grenade kills instantly. The the time you get before the molly full damage is applied is the time you are given to react to it, that's if you don't see it coming. The rifle grenade has nothing like this. Nothing like what makes the molly balanced.
The rifle grenade is bridled by nothing. Has no offsets, is easy to access and use. Its not even particularly expensive. And can be used against a variety of enemies. And is great on buildings as like just a plus.
Iam going to mention again, there is nothing here to show that this mainline unit needs an elite unit ability.