That trade system is absolutely useless, the majority of the stuff you'll find on there are hacked pkmn or just noobs looking for great stuff for some piece of sh** they just caught.
but luckily you are apart of a Pkmn theme forum, and shouldn't have a problem finding someone who is willing to make you a good/fair trade for what you desire.
Or there is the AR...if you fine with cheating. My first play through of Diamond I didn't really use mine too much till the end. and the main thing i hacked was a reasonable thing to hack. I hacked in the events to catch Pkmn like Darkrai etc since I know I'll never be able to go out to one of those Pokemon/Nintendo events to go get it form them. After that I tried the Wild pokemon Modifier...which is great cause the pkmn (from what i can tell) look and stat legitly.
But hey who knows, maybe come the next generation or when the Silver and Gold remakes come out (they better make them *shakes fist*) they'll make the world wide trade system better and more reasonable