I have run plenty of times when cunning gear would drop with no IA in the group, or aim with no BH, or strength with no warrior so no it is not aimed at classes present.
That's crazy. My experience has been the exact opposite. I even soloed TBT or the Esseles with all of my characters around level 12-13 just because I was all but guaranteed to get the blue/orange drops for my PC. Heck, I soloed TBT with my Bounty Hunter like 3 times trying to get the Operative Jacket for Mako and I got NOTHING but AIM gear each and every time.