The Tank is not guarding you is the issue, not only does guard reduce the damage you take it also greatly reduces the aggro you pull, and healing aggro is pretty big, especially if your taking on 5-6 mobs.
Always make sure the Tank has Guard on you....
The other issues are usually tank related like the Tank not using his taunts.... We ran SM EC the other night and the pug tank didn't even know he had taunts so he wasn't using them... Thats the problem with a MMO that lets you solo pretty much all the way to 50.
The only time a Tank shouldn't guard you is during a Boss fight, then he guards the hardest hitting DPS so he won't pull the boss from him, but for all trash pulls make sure the healer is guarded.
This is not correct. It would take a totally derpy tank to allow a healer to pull aggro on something he has aggro on. The only mobs that will be attacking the healer are ones that were not picked up by anyone at all, so reduced threat will not help if you have the only threat. Guard is much better used on the top DPS who may actually pull aggro from a mob that the tank is trying to hold onto. There are very few fights where guarding the healer is the right move and none of them are a part of a FP.