Do you have a couple of favorite sellers you frequent? I've seen the poor reputation GSC has on eBay among members here but I'd like to know if we can share some sellers we trust and which to avoid. Hopefully we can share sellers that don't deal too heavily in problem coins. I'm kind of reliant on web purchases due to no good shops in my area.
I no longer know ebay sellers well enough to recommend someone but I do have a few thoughts. Dealers get stuck with problem coins all the time. It's how they sell them that's important. I trust those that list the coin as a problem and know what they are talking about. That and a good return policy make me feel I'm dealing with someone honest.
I buy a lot from Hocey. Have for several years. I buy mostly silver bullion or non-circulating sterling from him. Prices are usually close to spot, but I do bid on a lot that I don't win. He also sells a huge number of US coins in various grades , mostly VF or lower, but plenty higher, plus a lesser variety of world coins. He is an established dealer with a store in Michigan and almost 100,000 feedbacks.
People like to dump their coins on ebay for the fastest buck and some do quite well. Most of the stuff is grossly overpriced but deals can be had. I know my local coin dealer dumps what he CAN'T sell on ebay if that tells you anything.
This is meant only as a general addition (nothing against the mentioned seller), but feedback can be and often is meaningless. Unfortunately, some of the worst offenders/dreck peddlers on eBay also have stellar feedback, and is why reading between the lines is often a better indicator of a seller's trustworthiness.
You also present yourself as an astute buyer. Most scams happen because people get greedy. Common sense is the best defense