Interesting subject and good comments all. When I think of a "balanced" ctg., I usually view that in terms of what powders I have and the performance level I want to reach for the purpose intended. That being said, when I look at a mission I want to accomplish, I tend to view that in terms of what MIGHT happen, such as seeing a huge boar unexpectedly while pig hunting as my cousin once did, or maybe a bear in bear country when you're only intending to hunt deer. Like the Boy Scouts say, it's wise to be prepared, and that includes the calibers and rifles you carry afield.
For deer, I'm with Hogtamer on the .270/130. It'll never fail unless bullet placement is pretty poor. The only thing that might be better on our little Southern whitetails is the .25/06/100 gr. Yet, my son's 6mm. Rem took over 30 deer, all with a single shot with the 85 gr. Speer BTSP, and two were just over 350 yds., too.
For big hogs that CAN, if they get a mind to, hurt you, I'd really prefer my .45/70 guide gun, or at least the .44 carbine. They're in the woods here and long shots aren't likely at all, and mostly impossible, but up close and nasty would always be a possibility. We're also getting some bears in my area now. 3 have been killed on the bypass by cars in my town, so any time I go to the swamps, I like to carry a .44 pistol, just in case. Never know when you might blunder into a sow with cubs. Not likely here, but certainly not impossible.
As to what constitutes a "balanced" ctg., it all depends on the performance level you want, and what powder you want to use to get to that level. In 7mm, if you want to use any of the med. burn rate powders, the 7x57 and 7/08 like my grandson's area about ideal. Good velocity, great killing power, and a nice balance of bullet wt., hole size and usability on a huge variety of game just by picking the right bullets for the purpose. For deer, our little southern whitetails always seem to respond most readily to the lighter, thinner jacketed ones. We almost always hunt from tree stands and generally have time to wait to get a broadside shot, or nearly so, and don't need a lot of bullet wt. or penetration go get through their back ends, etc., so it just works best to use the lighter, faster expanding bullets and just place them well forward of the diaphragm, preferably right on the little crease behind their front leg, about 1/3 of the way up from the bottom of the chest. If one takes one of these and runs off, it's probably because you hit the heart, and it'll run out of blood & O2 in about 50 yds. It really doesn't take a "controlled expanding" bullet on these smallish deer. The .308 is a great caliber, expecially if you want a short barreled rifle, as is the .30/30 on deer. The great thing abou the .30/30 is that every RN or FN bullet made in .30 cal. is made expressly for the .30/30's performance level and velocity. They penetrate and expand very well in all makes that I've seen, and they've been all the standard makes.
If anyone can figure it all out, they're a lot smarter and more experienced than I am, and I have no problem at all with that. A lot of what I know also comes from a friend who has shot more deer than most people have ever seen. He's done an awful lot of cropping problem herds for farmers, and I've hunted with him often, and he's also the best natural shot I've ever seen. He's a big fan, for deer, of the .25/06, .270, 7x57 and 7/08. He doesn't like the magnums, and his experience mirrors my own in that they tend to have more deer run off after the hit due to the "controlled expansion" nature of the bullets used in them. And all the while a .25/06 or the others will almost always put them down in their tracks with a good hit. It seems counterintuitive, but when you think about it, it makes at least some sense. Maybe there really IS a thing called "overkill" after all????
I do also think that when all's said and done, it's the hunter, and not the arm or caliber, that makes the most difference. A good hunter with a .22 RF will eat venison, and a tyro with a .458 will go hungry, most likely.
When I go into the woods now, I always like to carry something that'll deal effectively and very quickly with a wild or rabid dog or coyote, and in the swamps, with up to a bear at close range. They normally shy away from people, and are almost never heard as they make their escape, but they're there, whether they're seen or not, normally. For me, it just winds up being a matter of choosing what it might take to survive and come home and do it all over again. For me, I guess that'll always be what I regard as a "balanced" caliber choice.