Long distance throwing of grenades is no doubt largely borne of experience. Grenade mechanics have been the same since CoD4 - you learn how much to cook them or not and pinpoint accuracy is just a matter of practice, hence if you've been lobbing frags since CoD4 then you've probably got it down by now.
The ease of avoiding grenades, to put that point into its true context was specifically around that map, and the start of the game. Avoiding frags at the beginning of Dome at the A flag is easy. Either don't rush forward, or whack up your trophy system etc, although as I said, I don't think I've ever been damaged further than a hit marker at that point anyway. For the rest of the game, and on other maps, yes grenades kill you, but my personal experience of MW3 is that this is no better or worse than previous versions of the game.
The ease of avoiding grenades, to put that point into its true context was specifically around that map, and the start of the game. Avoiding frags at the beginning of Dome at the A flag is easy. Either don't rush forward, or whack up your trophy system etc, although as I said, I don't think I've ever been damaged further than a hit marker at that point anyway. For the rest of the game, and on other maps, yes grenades kill you, but my personal experience of MW3 is that this is no better or worse than previous versions of the game.