Many recommend Fury Warrior, but in your place I would avoid it. Not because it is hard to play, but because it is hard to gear up - like all arp classes. And because there is bunch of them on the server geared above 6k. I often create 8/12 hc pugs and I can tell you that first classes that wisper for inv in one minute are overgeared warriors, which will make less chance for you to get invited.
Classes that you usually find last to fill up your raid are balance druid and demo warlock. Sometimes shadow priest. From those 3 class/specs you should chose your toon. They are all easy to play and due to their special abilities they are "a must" in every raid. Gearing is significantly easier then fury warrior since both spirit and haste gear can be useful to you. Balance druid being easiest due to bis relic which you buy from emblems. SP an Lock need heroic ofhand and wand. But still way easier then warrior.
Other than that, if you are into tanking, Blood Dk would be good choice. It is easy to gear and easy to play. He has braindead single target aggro and emblem sigil, compared to paladin which needs shield from BQ. His bis items are almost all on trash bosses like Lord Marogar, Rotface, Fester and Valithria Dream Walker.