Just turn it back to how it was before, but leave grenadiers alone. In this way, it cuts down grenade spam, while still letting grenadiers lay minefields quickly (which was the aim in the first place).
I see no problem here(aside from nadeing in emp_district). You're once again trying to kill a fly with a bazooka...
On some maps sniping is powerful, others assault rifles, others grenades, and on yet still others, turrets or vehicles... Listen! Every strategy lends itself well to a certain type of terrain. Wide open sprawling maps can be dominated by light tanks, tight narrow alley ways are easy death traps for mines and MG's, laying a constant blanket of grenades can also be devistating but seriously... I play district and usually watch while scores get mowed down by grenades. I usually have a good ratio and use all 4 classes. I seldom die to grenades. Most people who do simply aint paying attention and don't learn too fast. I won't mention any names, but on District a couple days ago I watched one guy get over 100 kills mostly with grenades. He also got about 50 deaths. I got about 60 kills with 8 deaths using different classes over the course of the map. We both had similar net enemy kills over deaths, tho my ratio was better. Most of the people who died from his grenades ran into an area over and over where black pock marks and continuous 'booms' clearly indicated grenades going off every few seconds, yet into that spot they ran and died over and over. I killed that same genade thrower a few times using mortar, assault rifle and yes, I think on one occasion a grenade. I never did get hit by one of his grenades in that particular game because I was paying attention. It's not the grenades fault if you can't be bothered to move out of it's way. It's not the sniper rifles fault if you stand still out in the open on a big map. Develope counter tactics. Be aware. You'll live longer and die less. My big gripe about that map is I keep getting stuck inside a wall or some crap on respawn. Happened to me 3 times in a row earlier and I finally got frustrated and left the server.
