There were a number of posts about potential cheating and/or irregular drawing in a few tournaments in the last couple of years. Some people have related that they feel that there was no way to prove someone was cheating, and that feeling like they might have been cheated tilted them for the remainder of the tournament.
Deciding in advance to call the director each and every time achieves a few things:
1) it informs your opponent that you want the rules enforced during your game.
2) it gives the director some history over the course of a tournament and even over multiple tournaments, should the TD list be used. Yes, one poor drawing technique moment is not actionable (and likely should not be unless obviously just plain old cheating). 3 or 5 or 10 might be.
3) The onus of "should I have acted? I hate myself for having let this person cheat me (maybe?)" is removed.
4) The *decision* during the game of "should I call the director?" is removed. You make the decision in advance. The director will do what he/she wants to do--but regardless of the decision, YOU have done all you can do. There are bad calls in sports. I think it's easier to get over a bad call than a "I didn't do anything and got cheated as a result" feeling.
As an aside, you don't have to be a dick about it at all. Just when you see irregular drawing, call the director over, inform the director and the player quietly about it. And do this every time the drawing is irregular as neutrally as possible.