Issue with MacBookPro11,3 (dGPU) and 4K Display

I encountered a strange problem with my Macbook Pro late 2013, GT 750M dGPU and 4K Displays (I testet different brands: LG, Dell and Nec):
sometimes the display won't go to sleep mode after shutting down the Macbook, sometimes it won't wake up, bluetooth began to loose connection periodically, the image was noisy.
I reset SMC and NVRAM, but it didn't help.
I then had the chance to test one of the displays with another exactly the same specced Macbook and there where no such glitches.
So I'm pretty sure that my specific Macbook has a problem with the dGPU.
I made an appointment in the next Apple Store and the friendly support technician offered me a repair for 660€ (roughly 720 US $).
I wasn't very happy about the prospect to pay such an amount of money for a repair since the Macbook is less than two years old, in pristine condition and I am pretty sure the problem was not caused by anything I did. He the recommended to email Tim Cook directly which I did in November last year but unfortunately I didn't get any reply.

I did a little bit of reading here and discovered, that MacBooks with a dGPU are prone to problems of different kinds, that leaves me with two questions:

1. is there any chance I can get my Macbook repaired without paying this much money?
2. if not, would you recommend to buy the next Macbook without dGPU? I do mainly graphics design on my Mac, But occasionally I work with After Effects too, wich should benefit from the extra GPU Power.