Hey now, that was super-creative! You just happened to tap into the collective consciousness of HP readers or something.
For me it wasn't so much that Tonks was all depressed, but the fact that there wasn't enough build-up to Remus/Tonks. It was meant to be a mystery and then when the other shoe drops you're supposed to be all "Oh, so THAT's what it is!" but most people ended up going "WTF? come out of nowhere, much?".