Nope, it isn't as easy as you say.
If there's a dude running at you with the SOS and you see him when he's so close that even if you aim your rifle and shoot right away he might come into gib range and kill you (and that happens a lot in this game because the maps are the way they are) you cannot escape from that, you can only hope he somehow misses the shot.
If you roll back, he'll approach faster than you retreat and bam, dead (this is what happens to me the most). If you simply turn back and run, he'll run behind you and the second you stop bam, dead.
About the CHECK YOUR CORNERS bit... it doesn't really matter if you check them or not. You know, you need to get close to them in order to check them and then, unless they miss, you're dead. The most you can do is take him with you.
So yeah, it's annoying and it sucks.