Grounding for Outdoor Outlet
Is it practical?  I guess the question is, "does lightning strike twice?"  

One problem is with near misses.  Lightning has so much voltage at biblical amperage, that it creates a voltage gradient across the ground.  Earth at your remote outlet could be 20,000 volts hotter than your house.  This is what kills animals; the voltage on their front feet is different enough than their back feet that a lethal current can flow through their chest. 

Without a ground rod, you hope the PVC and THWN insulation is strong enough to survive a 20,000V differential.   With a ground rod, you remove all doubt - you are grounding both ends of the ground wire.  That means the ground wire will be participating in this voltage gradient (helping to arrest it also). This has the risk of burning out the ground wire and having this voltage arc internally to the hot and neutral. 

So lightning is such a slippery customer that it's hard for me to call it "definitely good".  There are outlier conditions in which it could make things worse, as I described. But it's the way to bet IMO. 

Of course, since it's not a mandatory ground rod, it doesn't need to meet standards for mandatory ground rods like the 25 ohm impedance test.