Personally, I like the lightest rod and reel combination and I don't pay that much attention to "balance".
The concept of rod/reel balance is a carry over from spinning and casting rods. Since the line has very little weight in these two systems, the rod/reel balance point remains relatively constant no matter how far the cast. Your hand location is also fixed on these rods since you need a digit from the casting hand on the reel to release the line. You cannot move it up or down on the grip to adjust the "balance" point.
Secondly, and most important, the fulcrum of the cast with a spinning or casting rod revolves around the point where the rod is held. You flick the rod with your wrist. The weight of the bait and rod end on one side of the fulcrum actually does balance the weight of the reel and rod on the other side. Therefore, the balance point is a valid concept and much more important with spinning/casting rods and reels.
Additionally, the concept of a fly line mass alone balancing with a fly rod is incomplete because fly line velocity is much more important than line weight in flexing the rod. What bends the rod is energy and that is a combination of both line mass and line velocity. If we double line mass and keep velocity the same, the energy will double. But if we keep line mass the same but double velocity, the energy will be 2x2 or 4 times as great. So if we double haul, we increase the energy and momentum pulling on the rod tip without decreasing the line mass on the opposite side of the "balance" point.
Unlike a spinning rod that casts a line with virtually no mass, with a fly fishing outfit you are casting a line with greater mass. Balance is not static as you imagine it. It changes with how much line is out and also with the flex of the rod which is really the line's momentum and energy resisting the pull of the rod. So there is a force pulling on the rod tip. This force is no different than gravity pulling on the end of the rod except that it alternates with the to and fro pull of the line much like an alternating current. So how can a "rod" be balanced with a "reel" when this is a dynamic relationship that is constantly varying with the amount of line mass off of the reel, line velocity, and the length of the cast?
The longer the cast, the lighter the reel end of the rod becomes and the greater the variation of the force on the rod tip. I suppose that if you make very long casts on a routine basis, you might prefer a heavier reel to counter the forces on the rod tip but that does not mean that this is the ideal reel for another individual.
Unlike spin or bait casting, in fly casting balance will also vary with how high up on the grip, you prefer to hold the rod. Since the reel end of the rod is by far the heaviest portion of the rod reel combo, this affects the static balance point of the rod reel combo and determines whether the rod/reel combo feels tip heavy or tip light.
Finally, you are assuming that the "balance" point of the rod comes into play when we cast. It is really important only if the fulcrum point of the cast is constant at or near the balance point of the rod as it is with spin fishing.
When we cast, we generally keep our wrist locked throughout most of the casting motion so that there is no fulcrum point at the wrist or near the balance point of the rod. Most of the power and movement for the cast occurs at the elbow and the shoulder. So the extra weight of a reel is not behind the fulcrum with the rod tip being ahead of the fulcrum. In reality, with the major fulcrum points at the elbow and the shoulder when the wrist is locked, both the rod and the reel are on the same side of the major fulcrum points of the cast.
Therefore in my view, both the rod and the reel add to the amount of mass that needs to be moved in order to make the cast and this moving mass is on the same side of the fulcrum points. This moving mass needs to be countered by the muscles of our arm and shoulder which really provide the energy for the cast. Our forearm, and hand muscles provide the fine motor control that provides the accuracy for our cast.
This last consideration is why I believe that I find light reel and rod combos the easiest to cast. If you are a wrist caster, then the fulcrum point is at the wrist with the reel on one side and the rod tip on the other. This may be why you prefer a heavier reel.
In my view, rod/reel balance in casting is a personal preference without a single right answer. It depends on how we prefer to cast and the distances we prefer.
Balance in fishing is determined by where we hold the rod and what angle we want the rod to be at. For example, if short line or high stick nymph and we hold an elevated rod tip, an outfit that is tip light so that the reel is heavier is easier to hold in a tip up position. Then I can see that balance is important, not for casting , but for fishing!
In my view, rod/reel balance in casting & fishing is a personal preference without a single right answer. It depends on how we prefer to cast, the distances we fish at, and how we want to hold the rod. For most fly fishers that fish all all distances using all methods, balance is an outdated concept. What they will find least tiring is a tip light rod with a light reel to reduce overall mass that must be manipulated in casting and fishing.
PS - Fly rods are actually easier to cast without a reel. Go outside and try it buy putting the reel on the ground and you will find the Vincent C. Marinaro in my previous post is correct. You can cast further without the reel.
