I usually commend DPS for a few reasons. As a tank, I really appreciate feeling like the dungeon or trial is a breeze. DPS roles seem to play a large role in that as the better geared and more skilled DPS classes will definitely be more noticeable. I've had dungeons that have taken 20+ minutes and some that are close to around 15 minutes with a good group.

I also give commendations if they have cool glams or nice-looking characters. I also like seeing jobs that seem kind of rare such as MNK, MCH and DRG. I also really like partying with BLM due to the sheer fact that they nuke the shit out of everything. It's so satisfying to see.