You got to stand out to get a commendation. Usually I'll give mine to whomever was the most helpful to the group. So just by doing the bare minimum of your job you don't automatically get one. You got to go beyond that. Like giving tips or refreshers on old boss fights, or if you're a Bard spamming Peloton between big pulls, DPS doing big numbers making our fights noticeably faster AND using enmity reduction skills, Tanks doing big pulls and actually using their cool downs, Healers maximizing DPS while keeping everyone alive, ect. Being friendly is also a big plus. If nobody was particularly good at their job, but someone was super friendly and social i'll give them the commendation at the end just for the good conversation. This is especially true in the non-skippable cutscene MSQ roulette. Friendly and funny people make those runs so much easier to tolerate so if you're cracking jokes and we're having a good time you're going to get my commendation.