I don't usually target big fish. I'm out to catch fish, and if they happen to be big, great.
I do use a dry-dropper a lot. And while I've never thought of it as 2 dries, I guess it's the same idea. I do it on small streams a lot, often with a beadhead or something similar, and that's the classic dry-deep nymph, not much different than an indicator rig. But you really can't fish a "deep" nymph that way on a larger stream, it just pulls under the dry. So the dry-dropper rig on a large stream usually has an emerger, or a light nymph in the film, as the dropper. I guess that's the same idea as 2 dries.
I have caught 2 fish before, both on dry droppers, and on 2 nymph rigs. Usually it doesn't happen that 2 fish take at the same time. It's that the 2nd takes while your fighting the 1st. You've probably seen where, when fighting a fish, another fish follows it around? Well, if in the act of doing so, there's another fly dangling back there, they sometimes take!
Had a buddy once who had it happen with steelhead. He had an egg pattern and a stonefly nymph. One fish took the egg. During the fight, another was chasing the stone all around, lol. He landed neither, whole rig broke off, but the fish remained connected to one another for a few minutes and you could see them fighting each other!