There's no mechanics to discuss here, just about my misconception of what the Trainee set is about. Yes they drop on starter-islands like Strol M'kai, Betnikh etc. and I would just decon them because I felt I wasn't in training after around 1500 CP. HOWEVER, why was I going to XP farming spots with my level over 2000XP, to use up leftover time on my Aetherial Ambrosia session with my same old dungeon-running gear? I realized with the Trainee set so cheap at Guild Traders I might as well build a whole set for this purpose alone: XP farming and I'm so glad I did. For example, a round at my favorite XP grinding place before was a gain of 32K XP per round with Aetherial active (do 10 rounds and you get a gain of 320K!) I was doing that instead of questing where I was getting around 28K per high-XP yielding quest and to do 10 of those quest would take a LOT more time than just doing 10 rounds at my spot. With the full Trainee set I'm getting 49K per round! I just keep the set available whenever I need to use up Aetherial Ambrosia time instead of schlepping around. Mind you this is without the additional XP boost from the enlightened period you get at the start of every new day, the only XP boost are the 100% from Aetherial Ambrosia and the Trainee set for my test results. For those who avoided fishing calling it useless might want to take a second look, all that fishing results in Aetherial Ambrosia and it takes time and OH it is SO worth it. Fishing may be a joke to some, but not a joke when I'm flying by their CP count by leaps and bounds.
The leftover time on my Aetherial Ambrosia clock after turning in my daily quests (I only use Aetherial to turn in quests, not do them; I turn in around 10 quests at one time) was usually around 30 minutes so I would head straight to my favorite XP grinding spot and get over 350K XP gain after 11 rounds. With the complete Trainee Set I'm getting over 500K XP gain from 11 rounds. Yes fishing may be too sedate for some but the end-result of fishing is this: a bunch of Aetherial Ambrosias to boost your XP, trainee.
Once I made the decision to test the Trainee set at my XP grinding spot, at first I was going to transmute another high level equipment set. However that would have taken 450 transmute crystals (7 armor, 1 shield, 1 weapon, 9 x 50 = 450). What a waste of transmute crystals! I said to myself: "just buy the Trainee set that I was deconstructing all the time". The pieces were cheap, found them with null perspiration. I noticed a little drop off in damage done and a little uptick of damage taken, but all-in-all: null perspiration, not much difference; I was doing rounds in about the same amount of time.