Numbness is not normal, unless of course you're married..
Just couldn't resist, sorry. And no, it's still not normal. I'll agree with the firmer seat advice, it's worth a try. And on the topic of sore knees, it sometimes doesn't take much adjustment to make a big difference. I shifted my seat ahead about an inch (or less) and immediately felt more pressure on my knees. I was lucky when I got mine, everything seemed to fit me to a T, most aren't that lucky.
Try tweaking one thing at a time for a few days, and see if it works for you. You proabably just need to fine tune a few things and you'll be fine. Have fun !!