Take one of your teams of 5 through outlands and beyond into northrend.

Then assess whether you could actually face running all that same content again with a 2nd, 3rd, 4th team etc.

I think your choice of teams so far has been very good. The always capable and fun shammies and the excellent druids.

The temptation with RAF is to just keep going, and going and going, so as not to waste your RAF time. Realistically how many of the multitudes of 60 will you play further.

One alternative - level a mixed team consisting of classes you don't have already. Then you have a load of characters you can level and sub in and out and make interesting combinations with.