Shame that some tanks have no idea how to review who needs the guard.
All my dps toons are type 1 female bodies, all look delicate and fragile. I never get guarded even though they are all campaign, black hole and DG geared. I do my best to use aggro dumps, follow kill order and give the tank a chance to build aggro, so I am not really concerned about not being guarded. If I mess up and pull I know how to use defensive cooldown, dump aggro, pop a medpack and keep on burning.
However, I have found in the gree event, my character delicate looks has made me a target in the pvp areas. I have been attacked a number of times while doing the heroic. This has lead to my death more than once, but it has also lead to some really shocked attackers when I finished off the droid, and then hit defensive cooldowns and finished them off too. Commando with 100% health, that shot my infiltration shadow the entire time I was killing the three droids, must have been really shocked when I closed ground and took him down to 0 before I lost my final 10%.
Tanks don't have it any easier, there is no foolproof way to know who to guard in a PUG. Gear is obvious, but players abilities and knowledge of game mechanics are less likely to pull. I have been in HMFP and Operations where people are whispering to me excitedly they are pulling aggro from the tank like it is something to be extremely proud of. I, like most people, want to put out the highest dps numbers possible, but not at the determent of the group's progress. So when I pull aggro I feel it is the sign that I am playing badly.