WordReference does have a ton of valuable content and a vibrant community but as you mentioned, the user experience isn't that great. Thanks for the encouragement ;)
The irritating thing is that it took me months to find WordReference, as it seems like Google really struggles with decently indexing some language sites. To be honest, I can only speak for Polish as it's the sole focus of my foreign language studies, but it's been a nightmare to find more than a handful of decent resources online.
If you want to bring more users to the site, I'm not sure if it'd be worth experimenting with adwords. Throw, say, a few dollars a day at adverts that target phrases like "Why does French..." or "How do I say in German" and so on. It might bring enough users to give the site critical mass.
