The role of the GM is to be a disruptive force in the players' plan. The purpose of the GM is not to use or impose rules, that is just a means to an end. The more the GM is concentrated on the rules the less he'll be concentrated on the players, their needs, their desires and the adventure as a whole.
How focused on the players are you as a GM when using rule heavy systems?
The GM must set the long term goals of the party, he must read the player's interests from their minds. Build a long term goal that satisfies his players, and then stand in the character's way to achieving this goal.
The success of the GM is a delicate balance between being disruptive and gratifying players. To much disruption and he fails to fulfil role #2, to little disruption and he isn't doing his #1 job, disrupting.
Player interests, desires and fears are not random. Trying to fulfill the goals of gratifying and disrupting players with random tables is at best limiting.
The GM is nature, karma and destiny, but he is also the rewarder of effort and perseverance. The party than endures and overcomes the obstacles of the adventure should be handsomely rewarded. Overcoming obstacles must have a real cost, at great work and risk. To reward the triumph over a "balanced encounter" is no good.
The entropic GM is that who introduces disorder into the players' plans. A constant drip of "disruption drops". The trickle of these drops is important for the game. Too much and everything falls to pieces, too little and the adventure lacks substance and flavor Players work not to defeat the GM, but to overcome the natural tendency of things to fall apart. The character's efforts are invested in keeping things ordered when nature's tendency is to disorganize things.
I find the so called "balance", random tables and heavy rules to be contrary to this function. There is no "expected" outcome in life. Random tables will lead to random results and random interest for the antagonists of the story (read monsters, creatures, critters, etc). Too many rules will steal the GM's concentration from the players, their emotions and interests.
To succeed the entropic GM must turn his back to balance, and expected outcomes. There are odds for player success, but they're just that, odds. Not a set path or expected outcome. No encounter should be expected to end in any particular way. Random tables should be avoided except maybe for inspiration and to break away from some habits the GM may have. In other words add more entropy to the entropic GM, but not to set the path or outcome of an adventure.
All encounters must serve a purpose in some way at some cosmic level. Not just deplete the party of some resource, but open up a path or route for the adventure to take. In the grand scheme of things the party will succeed in banishing the daemon, but exactly how is the interesting part. The orc party isn't just there to slow down or consume some arrows or spells, it gives an option of not being attacked, to evade in some way that may lead into new discoveries and encounters. The defeat of the orcs may be more than just a military victory. It may shed information and alternatives to the party which they may or may not take. Visit a village, detour to a cave, explore some area or tower. Each event is a nudge in a direction the party doesn't want to go. Some in the general direction of their goals, others quite the opposite.
When you play the entropic GM and step away from "expected outcomes" and "balanced encounters" you add a dynamism that makes the adventure feel real and unique. No longer are your players going through the motions of rolling dice with the knowledge that they will prevail. The attention moves away from what will I roll or how many attacks will it take to overcome this, to what will this encounter lead us to or what will be revealed or what change in our plans will come from this action. To achieve this your mind needs to be free to read your players and not burdened with reading the rules.