Well, as harsh as it may be – there is a time of warranty. Outside of warranty you're on your own. If too many products are at fault Apple will most likely react and extend warranty for that very fault. But this is not because Apple is so nice to customers, it is rather a tough business decision, an investment to make the brand strong. People remember this and tend to buy and recommend Apple because of it.
In your case on the other side, the number of faults seems to be too small. Apple again has to make a tough business decision: save money and don't extend warranty or extend it to make a few people happy and invest in the brand. It seems to be not viable for Apple, so they don't extend warranty.
I am sorry for that. But you should consider that AFAIK Apple acts with this issue like any other manufacturer of computer hardware. In my personal experience I had the same issue with HP laptops from the cheap Pavilion series. I don't recommend that to people anymore either because I had two models break within 3 years, both just a week or month after the laptops were out of warranty.
On the other hand I still use an older IBM ThinkPad. It doesn't seem to break. And I still use older Apple Power Macs, which also seem to run forever.
Luckily my Mac mini 2011 (Macmini5,2) and the Readeon 6630 graphics card in it still works. I would hate to see it break since I run not only the current OS X on it but also Windows 7, Linux and – which was the main reason to buy it – Mac OS X Snow Leopard (10.6) with Rosetta for my PowerPC applications. This is unofficial but it works great.
If you think that there are a lot of users with graphics issues on the Macmini5,2 then you could or should try to make it more public, which may include to get it out on some of the news portals, like AppleInsider and so on.
You could like other sources here so that we can chime in to help your case, but I'm afraid that is all that can be done.
Don't get me wrong, I support your case, as well as I have a personal interest to have warranty should my own Mac mini break. But my experience with such issues just doesn't make me more optimisitc about it.