That's an interesting definition of the word "waste" - choosing no effect over a small effect.
Maybe you're suggesting that *everyone* do that? In that case, the effect of your vote is dwarfed by the massive effort you'll need to invest to get *everyone* to vote third-party.
What I'm saying is: be realistic; it's not so simple. Simply voting third-party is a waste, by any practical definition of the word. The effect is more negligible by an order of magnitude than an R/D vote. If you want to make a change, come up with a better idea and push that. Your position basically amounts to taking your ball and going home, while ignoring the millions of other people still playing.
Want to make a real difference? Primaries. A ton of people are going to vote R/D, and you have almost no power to change that. But you can change what R and D stand for. The differences between primary candidates can be immense - far more than the difference between "Generic R" and "Generic D".