If I recall correctly, the official word was to prevent people from abusing Alt F4. Why? Why would blizzard care. If someone is abusing alt f4, they will get what they deserve down the line. They wouldn't get much loot, much exp, and would eventually realize they aren't strong enough for whatever they are doing.
Honestly, the 10 seconds wouldn't be that bad if it actually was 10 seconds. Some people have done research, numbers have been thrown around, but it is not 10 seconds from a dc to when your character leaves the world. Most of the numbers I have heard of are 20-50 seconds.
I have been playing a different game that loves to crash. But, I keep on living because it instant boots. I have lost more characters in that game than in 1200 hours of d3, and thats KNOWING that I have the option to alt f4. Yes, I suck at said game, but typically when things go down hill, first reaction is to regain control.
It would be nice to hear an explanation other than to prevent the 1% of players from abusing alt f4. This is typical mass punishment, and it drives people from enjoying playing Diablo 3 hardcore. I can only do a run or two at a time on my monk, it's gone almost 300 hours without dying, but everytime I am on it, I have the nagging in the back of my head "DC is coming for you..."