A major part of this issue for most raid leaders isn't the time players have available to raid, its players that are unprepared when they do get the chance to raid, especially on afternoon or late night which are more casual.
You are better off spending some time a few days before getting the correct gems/enchants and looking up tactics than you are squeezing in that heroic or rep farm if you know you have time to raid the coming weekend. Its also more likely to get you picked if there are 13 signups for a 10 man raid!
What frustrates people is having to repetedly explain tactics for encounters that have been around for months.
My advice if you only have limited raiding time is know what to expect, you will get more out of your raid as you will not have to sit for tactics explanations which can be up to 20 mins on some fights, therefore you kill bosses quicker, kill more bosses and get more lootz! which at the end of the day is always fun! Looking up tactics is not hard core, its common sense.
Tankspot has comprehensive guides on all encounters.
"Uru, your dps was pretty Imba