Which class is more sought by others for groups, and therefore easier to find a group for – guardians (tank) or sentinels (damage)? And is it a big difference?

Well I'd say Guardian tanks are most wanted. I mean 99,9% of the players seem to play a DPS class. And there are always shortages on tanks and healers.

 

But really you should play the class which you want to play yourself

If you play tank on the guardian you will always be wanted since there is always more dmg dealers then tanks or healers. If you want to dps sent is slightly ahead since it is a pure dps class though guardian is def no slouch and very close in to sents in 2.0. However sents have party buffs like inspiration that are very sought after. Edited April 30, 2013 by AngusFTW