| I helped a whole 150+ guilds worth of people Onyxia attune then Kara attune. Some of them stayed, some left. It burnt me out. It made me angry - people seemed to think I owed them things just for being a tank. Tanks are not guild resources, they are people who are also trying to have fun.
Tanks can have many hobbies that they enjoy: fishing, cooking, questing, collecting pets, collecting event items, lurking, chatting to friends, guarding the farm, running flags, etc. Some tanks like to respec twice a week and do arena. They also need to do farming (for resist sets, bigger bags, enchants, pots etc), and make at least enough gold for repairs and consumables for the week. If they are tanking 25-mans then they already worked very hard to get their gear.
The less people nag tanks, the more likely they are to offer to help and not go hide on alts or lurk. If they know you, and you have had some good conversations with them, then even more likely. If you helped them with something (trying out ss spec in arena, bodyguard for fishing competition, getting something weird from ZG, etc) without immediately demanding help in return, then even more likely. Sometimes they just won't help - farming 5 more primal life for their nature set before the next 25-man may be what they want to do today.
You are always free to roll a tank for yourself and see what its like. :-)
P.S. If you drag them into a wipefest then at least offer to pay their repair bill, so they don't get zero items AND pay gold to help you.  | 
