Tends to be. His strategy against speedster's essentially boils down to "Stick 'em to me and deal with them once they're stuck on my body". Your first strike would have to be the kill strike, and unfortunately Gren's built to weather the worst of it. Fighting at range would save you from the melee trap, but then it's your weapon against his, and his is a Gatling Gun/Rocket Launcher/Flame Thrower. He's no sniper, but the AoE potential means he doesn't need to aim. He just needs to know where you're at and let dakka sort things out.