They won't fix that because it's not something that they control. That is just a product of network transmission time, which is totally out of their control. What you are seeing is not what your opponent is seeing, and the outcome is just what signal gets to the server faster. You're shooting at targets that have already shot at you, but the signal has not arrived yet to update you on your status. From the other guy's point of view, you're already dead, the death has been registered at the server, but the signal has been slow to get to you ... slow enough that the snapshots on your client have updated during the transmission time, but they have updated based on outdated information. The fact that the other guys aren't having a problem means that it makes no sense to blame the server. The server doesn't decide to be fast with some people and slow with others.
The solution is simple. Bail from that game. In my case, the next lobby is usually good and I'm ready to go. If you can't find a lobby that works ... apparently you can't go anywhere on the internet without going through some very congested switches (that, unfortunately, is totally possible). The claim that "I have great internet" has nothing to do with this ... you travel in the same lines and through the same switches as everyone else.
I am totally able to admit that this seems to happen a lot in IW. I'm not jumping to conclusion about why, however. I could easily see it simply being the speed and the nature of play in this game. Since everything is pretty damn fast, you need updating faster than ever if both players in a gunfight are to see anything approaching the same thing. The fact that two people who are far apart ever see anything like the same game actually amazes me. This could also be a function of where the servers are, and perhaps they are not as well placed as they could be. If they are in big data centres (and they almost certainly are) this shouldn't be a problem, though ... or everything using that data centre would have problems, and that wouldn't go on for long. The other thing is how many of the matches are hosted peer-to-peer ... that could certainly be a factor and that CAN be fixed. Thing is, I only hear about this in rumours. Actual useful information points to everything being dedicated servers in public matches (custom games like pro scrims are peer-to-peer).
Anyway, "it's the internet", things speed up and slow down ... always.