It seems a bit unrealistic to adjust 4 other armies to bring them into balance with one under-preforming army yeah? I understand where you're coming from I think, but it's going to be much easier to buff an under-preforming army than to nerf 4 over-preforming armies.
The whole purpose of the proposal is to make grens different, and better at their specific role, without seriously affecting the other armies. Literally everyone is going to complain if you try and nerf all the other armies based off grens being underpowered. Just look at how many people are complaining now.
Just because many people complain does not mean they are right.
Grens are a 240mp squad with limited hp. Cons on the other side are 240 as well and lack dps scaling.
Grens are already different. They have plenty of choice in doctrines to help them.