You should never have problem with finding people to go along with you in any random FB; i give you my trick which never failed me before reaching lvl 58 (which level people massively emigrate to the Outlands):
1/ you perform a /who with appropriate level (and class if you want); Ex: /who 牧师 30-35
2/you type an invitation that you copy (remember you can use CTRL+C and CTRL+V ingame); Ex: 好啊，马上要下雪色了，有兴趣吗？我们4个人了。
3/you spam your invitation!! right click on every name of the result and paste your invitation.
Advantages of the method:
*you clearly reach all the possibly interrested players of the server and only them (you reach them no wonder their location on the map, sometimes they replies they actually inside the target instance)
*It's the fastest way; this way is so quick that you should have sent at least 5 or 6 invitations before getting the feedback of the fastest typing players. Until Maraudon, you are garanteed to have a team within a few mins.
if you do not get enough, enlarge your criterias: you search for higher and lower level (higher lvl may sometimes be interested and lower level can still do the job as healer), you search for other classes that can perform the job (paladin as tank, drood as healer, etc...)
Before lvl 58-60, you dont really need any specific class, i saw shamans tanking in the monastery and feral drood healing in Maraudon (although a real tank and a healer is the very safe core of any group of course)
This method never failed me in France nor in China. After a few runs you will notice some people always have the same level as yours and join your party, you make friends and it becomes even easier to setup a party.
Hope it helps!
田畕畾畕田 - Mage Herborist/Miner/Grinder