That doesn't surprise me. BS going up against normal explosives often fails it you take a direct hit. If ever there was a perk that could use a buff that would be it. However, that's just how IWs game are made which is why I prefer to stay outside of their blast radius. Granted that isn't always possible to do but I can make it work most of the time just by picking longer line of sight routes when I'm going up against them.
In most game modes it's not an issue however in Search using DC is a cheap tactic and really frustrating to deal with because you don't re-spawn (except maybe if you are playing SnR). Also, the traffic is fairly predictable in Search and once the bomb is down, there is only one objective, it's likely in a small enclosed area and you have a very limited amount of time.
Explosives aren't useless without DC. Blast shield is pretty weak in IW games and doesn't work against a direct hit. The ballistic vest is actually stronger than BS in my opinion. However, you do make a good point that DC is a 4 point perk. If you are going to tie up 4 points on one perk it had better work.
Explosives should not require accuracy of a sniper rifle in order to get a one hit kill so yes they are useless with out Danger Close. Also Blast Shield is just broken against noob tubes I didn't killed by a grenade without it and when I had it on I died. Danger Close should be like it was in MW2 all it did was increase the blast radius because the explosives already did one hundred percent damage.
I won't argue with you on your first point. I agree that they shouldn't require pin point accuracy but they do. Or at least a lot of them do. The C4 and the IED both give you a little cushion to play with but the grenade and rocket launchers pretty much have to be a direct hit to get a kill no matter what the other guy is using. Understanding this I've gotten pretty good at pinging people with them and therefore I have no trouble killing people with explosives. So they work for me even though I agree that they should have a wider highest damage radius. I'm pretty sure in Ghosts DC doesn't increase the overall blast radius but it just makes the strongest point within the blast cone further out.