Magic Shoe? -No Way. Pick from an arsenal.
It's time to think of shoes like golf clubs. There is no magic shoe, but there is a right shoe for every situation. Pick from a variety in your closet to have the best possible run, and take your running to the next level.
I got pretty banged up last week when I ran the Millineum Trail. It's a 14 mile loop which is one of the most scenic runs in the area. It IS rocky though. It seems to be rocky enough that when you finish 14 miles, you feel as if you have run twice the distance if you're wearing the wrong footwear. I'm used to rocks, but this trail is FULL of those little ankle biters that you spend the day dancing over, on, and around. Spending a lot of time on this style of trail can take its toll on your joints, but there IS a way to combat these effects. Picking the best shoe for the terrain can help you have a faster run and allow you to recover faster. Some times, even the most efficient of runners need a shoe that offers some lateral and medial torsional support as well as plenty cushioning for the day spent on hard rocks. It's all about economy. By economy, I refer to the energy spent running. Expending the least amount of energy while running equates to faster times, faster recovery, and less energy. Most people only consider gait, (stride), and shoe weight when considering economy, but movement overall and joint fatigue affect economy greatly. Sometimes a shoe which provides cushioning, although heavier can aid running economy by allowing less extraneous body movements on rough and rocky trails.
Running on rocky surfaces is just one example terrain which demands a specialized shoe. The perfect shoe for rocks won't serve you well on perfectly groomed singletrack. You need a tool for every job.
Basically, there are many options out there to pick from for trails;
I'll start by describing the light and fast racing shoes, otherwise known as minimalist shoes. An example would be the New Balance 100's. A trail runner that weighs in at less the 7 ounces. Yeah, Minimal. I've used minimalist shoes in 50 mile ultras before, and on the flip side, there are 14 mile runs that I wouldn't consider using a minimalist shoes. It's all about terrain. Flawless singletrack, often mountain bike trails, and pea-gravel surfaces tend to cater to minimal shoes.
There are crossover shoes, such as the Pearl Izumi Peak XC, that are basically road shoes with nubbier tread. These shoes work well as road and trail shoes. I like to use these when doing a mixed run involving road and trails in our local parks with well groomed trails. They tend to perform poorly on gnarly trail, and especially in muddy conditions. These models often have poor support in regards to lateral and medial flex. They provide cushioning, which isn't really needed as much on nice trails but is needed on roads.
There is also "all around" shoes, which aren't too light and hopefully aren't too heavy either. Some shoes in this category can do it all adequately. These are what most people own as their one pair of trail shoes. Examples of do-it-all shoes are the best selling Brooks Cascadia, The Montrail Mountain Masochist, and the La Sportiva Fireblades, Crosslites, Etc. These shoes not only benefit runners who are tackling rough trail, but also runners who weigh more than the typical runner.
Start off by picking up an extra pair of trail runners that is the opposite of what you have now, although I still recommend going as light as possible in all situations. My all around performer is a Montrail Mountain Masochist which still weighs in less than 12 ounces.
Adapt to the trail, build an arsenal of shoes, and see where your running takes you!