Obviously heroic modes are harder than normal modes. If all you want to be is a warm body, we aren't going to succeed.
Some common sense guide lines, for the next raid, should be:
1)If you aren't using some sort of numerical tool to figure out gemming and gear, get one now.
http://rawr.codeplex.com/ is a good one for nearly every class and spec. If you have one you prefer more, thats fine, eye balling it is not. Unless you are idiot savant, you cannot compare the relative merits of many pieces of gear and gem combos in your head.
2)You must spec and gem your gear for PvE raiding(stamina gems in dps gear are an example of things that don't work), single target dps(if you are dps, trash is not heroic) and major raid buffs (dest warlocks with out replenishment come to mind, please get it).
3)Read about the fights before hand. If you haven't done it on 10 man, watch a video. We don't need to wipe so you can see something for the first time and goggle at it.
You should have enough of an idea there IS NOT a massive explanation required. You should know what is happening BEFORE you get there (and yes reading and a video will make this possible).
In this case, Marrowgar, Rotface and Blood Queen.
Through out your life advance daily, becoming more skillful than yesterday, more skillful then today. This is never ending. --Hagakure