Looking for a class wanted by groups.

[Sarius]

The best thing would be to create a class that isn't solely group dependent. I would recommend enchanter, bard or shaman.

[Lojik]

I've thought about this before. One would think that the best option would be cleric/tank/enchanter, as these are generally necessary to form groups, however these classes don't stack well, and it can be pretty cyclical as to whether you will get groups. Some days you might be the only cleric, other times there will be several LFG in one zone. I personally think a DPS class would be easiest class to get a group for, as a group will usually want 2 or 3 DPS per group. No one generally has objections to a rogue joining their group, as they do awesome sustained DPS and have a positive experience modifier (however slight.)
After DPS I would tend to say enchanter would be a great option...there seems to always be a need for them.