Tough call, because you can't get around the auto-decline. If I'm worried about my offer being perceived as a low-ball I will put a note on the offer explaining my logic, like you did in your post. I suppose you could do the same thing in a message to the seller if it auto declines. In this case it sounds like he's not sure if he wants to sell the card or not. Some people you just can't reason with.
I collect Dany Heatley, Nicklas Backstrom, all Red Wings and most Yankees.