Wish I had joined this party earlier, but I've been on a key in Florida without wifi for two weeks. Just back the other day and haven't had time to post.
Some that I track and others on the OP list:
Lyman Bostock Jr: Not terribly tough to come by and there are usually a handful on eBay if you want an example. You might have to wait for a particular year to add it two your set, but even 78's pop up occasionally. I assume he was a great signer before his death.
Joe Desa: Tough, especially on Topps. I might see one a year. His 86 Donruss seem to much easier to acquire.
Bo Diaz: Not especially tough until you get to 1987. He was a great signer TTM from what I've heard. I've added him to my early-mid 80's set for less than $30 often. 87's are tough to come by because it's the most widely collected set, but can be found. 88's don't pop up often. I've seen one authentic 89 Topps and one 1989 Fleer sold I starting watching a few years ago (didn't save a scan of them.) I've never seen a signed 1990 Topps, Donruss, or Upper Deck. I doubt they exist, save for maybe 1 or 2 examples. They only purported sale of a 1990 signed Bo Diaz I've come across is a 2011 Collect Auction signed set that included Bo Diaz and although they scanned about 30 cards for the website, they didn't seem it necessary to scan the most important card in the set which I found odd because Collect Auctions handles more signed cards and sets then any other auction house and they would have known how rare it was.
Steve Macko: Ultra rare. The heavy hitting set collectors I know always quote between 2-5 examples when they talk about it's population. I've seen one I believe is good and haven't yet seen one for sale since I started watching. This card is near impossible as Ezcano is tough too.
Win Remmerswaal: Very Rare. I think this card is in the 15-20 authentic signed examples range. It's the "famous" tough card from 81' but the Macko is tougher and Anderson w/Craig is impossible. With the those two however, you can get Martz or Biercevicz for cheap and call it a day. There is actually a Remmerswaal on eBay now that I've been debating pulling the trigger on but I'm not 100% liking it.
Authentic:
on Ebay:
Ricky Wright: Tough and expensive. Not as rare as Remmerswaal, Macko, and others, but he's jacked up because he's in 87 and when his 87's come up they get bid up. Probably the most faked tough 80's signature. I wish this guy would just do a signing already...
82 Fleer Garvey: He won't sign it. A member here bought one raw on eBay and got it slabbed a few years ago. I didn't keep a scan of the card, but I remember not liking it at the time. Could be wrong. Haven't seen one I like since I started tracking it. Probably a $1000 card 100% authentic, but I made this for less than $10. It'll work for me.
1990 Leaf Kelly Gruber: He won't sign it. Signed some for his kids. This set is becoming very popular with set collectors and will probably become the next Garvey. Haven't seen one, but also haven't been watching as I don't collect the set.
1986 Topps Doug Flynn: Doesn't sign it, except for rare occasions. He signed 5 a charity auction for $400 a pop when pressed to do so. They were the only five on the market. One of the guys who bid $400 convinced him to do more signings for that particular card at the same price (he says it wouldn't be fair to those that bid $400 if he signed for any cheaper.) So it's tough, but if you need him for your set you can get him - once a year for $400.
THE IMPOSSIBLE: 1981 Topps Rick Anderson, Greg Biercevicz, Rodney Craig: Doesn't exist that I know of completely signed. Anderson was a recluse after 81 and most know his story. Rodney Craig was a terrible signer during his career and was homeless with mental problems for a long time following his career. I've seen one authenticated example featuring Anderson and I don't like it. The legend is the former owner of the authenticated Anderson tracked down Craig and set up a signing. He showed up, freaked out, and left. Six weeks later he was dead. The owner then sold the card, I believe KO bought it for $3k +. From the only photo I've seen of the card, however, I believe either A) it was signed by former Mets/Royals Rick Anderson, or B) someone forged it in the vein of Mets/Royals Rick Anderson because they were sloppy. The original owner had an amazing collection, but the signature was so atypical I couldn't accept it. Far as I know, this card doesn't exist.
The authenticated Rick Anderson:
There are other's but I just realized it's 3:30 am here....