Nobody likes to think they make mistakes when fishing, especially expensive ones. If you get a chance you should check your fighting technique on video, it is most revealing.
Some rods are rated with max drag and others with fighting drag, my point was that a max drag setting cannot provide you with a wide margin for error, one that probably will occur sooner or later, perhaps with unpleasant consequences.
A setting of 15kg does not sound much higher than one of 12kg if you say it quickly, however, in percentage terms the difference is obvious-25%!!
My advice would be to buy a rod with a higher rating than you think you need, running a rod at 75% will hopefully allow for most mistakes made by experienced jiggers.
Neil