CharlesGrey: You basically have two options:
1) Stop buying brand new games on GOG, and wait until the devs had at least a few months, perhaps better a year, to deliver patches.
2) Use Galaxy, their totally optional™ gaming client.
Olauron: There is the third option that I'm using myself:
3) Don't patch games
Actually, I don't use patches even in those rare cases when I use Galaxy. New games often have a lot of patches but require them only in case of game breaking bugs that make game impossible to finish. Luckily game breaking bugs are not so often so in most cases patches can be ignored until the last when I download the latest version to offline backup folder.
Problem with this is that sometimes the last version is worse or has problems that a previous version do not have. Or it has deleted features or unexpected changes to gameplay, or you have some mods and updating can break your save...so you want to keep that exact version, and it's not the last one (and the last one is not always the bug free version)
I use to just download the whole thing again, but that's because i can (have a decent connection). It's also a pain for us even with better connection than others, because if we want to keep some previous versions, we are forced to keep whole games repeated, and it's a lot of space.
I will add to the initial examples the Battletech game. I will have to check my external HD but if i remember well, the first 4 version patched or so we didn't have a single patch (and this was, imo, more than enough time for GOG to create the offline patches, maybe 7 or 8 days and for a game heavily marketed since the release) so i had to keep all the versions as whole games. Also, constanlty download those big games contribute to suffocate the download servers, and then you can see a gigantic thread about gog slow download speed.
It really seems the new biggest releases are a problem for GOG. Once upon a time, when all were little old games, this was not a problem. But actually we have 30-40GB new games that are more complicated to manually patch (i mean, to create the patch) and probably GOG is not liking this and regret having to do (but they promised Galaxy was optional, so we need those patches and they need to do the work anyway)
So it's a problem for us and for them, imo. And this will continue to be worse as the games get bigger and bigger (and have big 0-day patches because game was in a bad state, have not enough dedicated QA before release, etc, another typical issue from these days, specially with expensive AA or AAA games, ahem)
About keeping all the old patches, sure, you have my vote. But it's also a big problem, again because the number and size of all the patches for the big games. I prefer GOG over Steam not only because DRM-free, but because this classic...eh, "offline" installers and their patches that allow me to choose which version of a game to install and to play. And this part is also important for me, so i continue to download whole games if i don't have those patches, but that is not only time and work, but also a lot space in my external disks, and i just can't keep buying new external disks only for GOG.
So, i agree we all have a problem with the patches, and i agree also that a bit of info/clarification from GOG would be good for all.