This new system is an improvement over the old one. Whereas the old one had an initial discount on a single game purchase and only increased to the full discount if you bought all the games in the promo, this system allows you to increase the discount even if you cherry-pick your games. (So if there are one or two games you don't wish to get, you'll still get a greater discount than buying all the games but one in the old system)
But seriously, people on GOG complain TOO FREAKING MUCH! For all the good stuff you get out of GOG, I find it's completely worth paying the full price for a $9.99 game that I might get on steam for $7.99. (Oh what a huge price difference!) But GOG goes on and has promos anyway, despite the already low price of the games. Valve is a bigger company and Steam is more lucrative at the moment, so of course they can afford to have steeper discounts. But GOG provides stuff that Steam can't, most notably not being a games-for-rent service.
So how about we improve our attitudes just a little. If a GOG has a sale that may not be up to snuff in comparison to a Steam sale, just be glad that they are having a sale. (And no BS about "Well, GOG needs to know how we, the customers, feel about this." I'm fairly certain they want to give us the best deals they can, and you don't need to tell them that Steam may have a better sale going on.)
Also, if you already own a game that's on sale, THERE IS NO NEED for you to say "Sale sucks, I own this game already," or some variation. Instead you can say something like "I got this game and it's a great one" and maybe pitch it for the folks who don't have it yet.
GOG's community is one of the better ones out there, but people really do need to improve their attitude towards the things that GOG tries to do for us. It's rather discouraging to see so many complaints whenever I come to the forums.