I have a rare personal shield and a rare phaser weapon. I noticed I was getting my butt kicked worse than usual and was hearing 'personal shield low' frequently. I went up against a Klingon commander and pulled out my rare weapon. Or so I thought. Suddenly I'm weaponless and just swinging punches at the Klingon. I think he stopped to laugh. Then I realized I had no shield. I had to steal a common personal shield from one of my away team just to survive.
It seems that the ground related rare items are broken.