Yeah, it's usually better to sell individually, but it wouldn't hurt for you to try to sell it as a lot first just to see what happens. There's occasionally people out there who are contemplating getting into a new Star Wars collecting subline, but don't want to go through the whole hassle of buying it all separately. Picking up a large lot can be very enticing in that respect, even if the price tag is rather hefty. But even if the lot doesn't sell, or you don't get the asking price you're looking for, you'll at least get some preliminary solicitations on some of your individual pieces so you'd know where you could start with those if you resorted to that method.
As for worth, are your figures still MIMSB, or have they all been opened and displayed? If it's the former, I'd just ask for the original selling price of $20, or perhaps cut them a little discount and just go with $15. If they're opened, but you still have the box to go with them, I'd say $10-$15 each. If it's just the loose doll (complete), I'd probably say $10.
I don't collect 12" myself, so I'm not sure if any of the standard issues would be deemed VHTF, in which case I might ask for a slight premium on those. Maybe do a quick scan of the completed eBay auctions on all the respective figures to find out.
How many of the 12" dolls do you have altogether?