Actually, I'm running a 2011 MBP 17" that just went through the free logic board replacement for dGPU issues, after the dGPU just died while playing D3.
I also upgraded it, current config is i7-2760QM, 16GB DDR3 1600MHz, 512GB Samsung SSD, ATI 6770M dGPU.
Compared to my work rMBP 15" mid 2014 which is quite similar in config (i7-4xxxHQ, 16GB Apple DDR3, 512GB Apple SSD, GTX 750M dGPU) in day to day use (as a developer) I feel no noticeable difference.
I started pondering now either getting an eGPU setup with AKITIO and GTX 970 or a full desktop PC, I was afraid that TB1 and already having a dGPU will make things not worth it, but from your post I see it is totally doable.
So thanks for that.
That is very nice to hear, guess windows 10 support and drivers are way better because of the official support for eGPUs on TB3. I am considering getting the Razer enclosure because of TB3 (yes, I know I have TB1 currently, but that means I could use it with a different, newer laptop aswell) and the fact that it can hold a big GPU and has the built in PSU. About RAM and SSD, I did those upgrades a while ago. They were pretty straight forward to do, but the SSD especially speed it up a lot. Originally it had 4GB RAM and 750 HDD.