I resubbed a few months ago to do the CM's and it was probably the most enjoyable time I've spent in WoW since the end of Ulduar. Just look up which gear set is optimal for you (Amount of gems, correct stats) and go buy some invis pots from the ah, about 100 of each. I did a few of mine with friends but most through oqueue random groups.
Don't get me wrong, many of them were fucking hard. But none of them seemed insurmountable. I was a DK tank though with probably optimal gear setup, I hear other tanks have less of an enjoyable time.