I understand that training is not an exploit nor violating the rules of conduct! Keep in mind you and I may not be on the same server.
Lately, regardless of where I go… Whether its cursed shore (mad ori rush) or the mad king’s labyrinth (train to the zerg), training seems second to breathing. I only had the urge to write this because recently, I was trained 4 times by players who are trying to reach zergs in the labyrinth. Unlike my 80 ranger, my 11 engineer struggles to deal with over 4 mobs with low level gear 
The first few weeks players were pretty courteous and I rarely got trained. If I did get trained, the player would return to help kill the mobs. However, the past 2 months or so I continuously get trained wherever I went and players VERY RARELY stopped to politely taking care of their mess. It seems as if people are intentionally taking advantage of the aggro mechanics; running the mobs in front of people they wish to train so that they can: reach an ori node/reach a zerg/reach an event/be sadistic all without clearing mobs and leaving it to the poor soul they trained. I am generalizing behavior of SOME and not all players, it is still very irritating /frustrating and perhaps could use an adjustment. I’m not sure how the system could be adjusted but, if anything can be done I think certain players would welcome the change!
Tl;dr: Training is sometimes very irritating /frustrating and perhaps some adjustment can be made to avoid training!