I have to agree that the quick simple /tell before an invite makes a huge difference. I've often regretted the blind invite PuG, as it usually winds up being poorly led. I have on ocasion come across the poorly led PuG with the /tell, but it is less often.
The most important thing to put into the tell is the level range (IMHO). If your looking for something in particular (like a healer) that should also be included. Remember not all defenders are healers (my kin/ele is a buff/debuff maniac, only 1 heal).
