Rifle grenades received a serious nerf in the last patch - I wouldn't hurry to call them OP now. Au contraire, for their price they kinda' perform like shit.
situational, gotta target the spot where they bunch up the most, sometimes u strike jackpot and shave 5 models off a squad, sometimes its one. though, on the average its about 3 models for each rifle nade. on top of that, they have an awesome range and fire from safety, difficult to watch their animation when they can just fire off from their current position. i wouldnt call all that 'perform like shit'.
similarly, molotovs insta burn models on impact, sometimes one, sometimes 2, sometimes no casualties, just a small bit of hp. pretty rng based.