It is quite possible to mine and acquire items from the lowest of Unspoiled Nodes (which DOES include Darksteel and Clusters) before you reach level 50. I did so myself when I first leveled Miner. You won't have Toil, so you'll need to dig through the clutter (it will take 2-3 swings to dig through), but you CAN successfully gather materials. It's just not very worthwhile until you get level 50 gear and Toil.

For a newbie Gatherer, though, I can certainly see the appeal of hitting up those Unspoiled nodes as soon as you're able to detect them, however poor your yield. It can definitely give you a sort of "I'm in the big leagues, now!" feeling when you collect your first Darksteel Ore!