Then you need to either find a new tank or teach the tank you have. If he can't effectively use his CDs or fails to properly mitigate damage then he is a terrible tank and should not be tanking.
None of us are overlooking the rest of the group. The problem is that no one wants to tell someone they are failing because they don't want to hurt someone's feelings. So if your tank fails then you need to man up and tell him.
Then work to improve your family/friends/guild skill level. I can show you a number of players who have done this. I have done it myself my previous guild was not so great, the GL just let people he knew into raid not caring if they could down content or not and I put my foot down along with a few other raiders and stopped it. Guess what happened? We got better over time to the point where finally we were pushing through content and people were getting better at their class/spec.
That's what the LFR was made for, to allow people with time constraints and other issues pressing on their play ability to see the content at a much reduced difficulty. Why give them the opportunity to complete normal and heroic DS when they still get to see all of DS already?
This really has to stop. A lot of you need to be put in a tough situation for once. Some of you need to have your guild disband tonight and your only choice of available raid spots is a pretty terrible guild.... You need to see what it's like to be held back because of other players, and because the better groups, who only have room for so many people in each raid, are full.
You need to accept that life happens in WoW, and sometimes it takes nerfing content to be able to get the people who should be doing the un-nerfed content a chance to actually do it.
This is to help success not come at the cost of having friends or family. Like I brought up a few pages back... to be successful in this game, you have to be ready to tell your mother, or your daughter, or your girlfriend that you're not playing with them anymore because they're bad. Do you REALLY not think theres a little problem there?
WoW is a raid or die game.... You have a choice, sacrifice everyone else so that you can raid, or choose to have friends and spend literally the entire time you're on your 85 just running around SW and Org because it's not like you're raiding and getting anywhere.....
I must say you are terribly wrong. I've been in some pretty bad guilds, I have taken some bad guilds and turned them into raid guilds. How? By telling people the truth, forcing them to improve and getting them to play at a higher level to therefore down the content the way it was introduced. Will it take longer? Absolutely but you will feel better about accomplishing it that way.
Now those of you who have time constraints and such have the option of the LFR which lets you see the content. Don't say "But I want the gear!" because if you aren't willing/able to put in the effort to get the gear then you don't deserve it. You pay $15 a month to play the game, you have the opportunity to get the loot if you are willing to push through the obstacles. I hate seeing people needing their hand held through stuff that is already easy.
If your a great player then push others to be great. The idea that you can't improve a player's skill level even if their time requirements are crappy is preposterious. Teach them about proper itemization, rotation even help them with enchants, gems and such! I've done it all before and I've probably sunk a lot of money into guilds that I am no longer a part of to help other raiders succeed so that as a group we succeed.