I'd love to buy a 6Dmk2 to replace my 80D. That would be like an upgraded full frame sensor with 80D specs ...minus degrade in max shutter speed.
6D and mk2 version is "smallish" for a mirrored body.
Please use an X-T2 on a low lit dance floor with flash and compare it to a 5dmk3/6D or even a Rebel series with a external speedlight using the red focus assist grid beam. You'll instantly realize there's a MASSIVE difference in AF performance. I have full confidence in Canon in that low light performance. I do not and will not use my Fuji X-T2 for that type of situation as I get substantially more hit rate with Canon in low light.
Casual photography the 6dmk2 is expensive right now but it's truly a very good camera "for what it is".
I am definitely buying one so I will get first hand experience I am not going all in *LOL* Time will tell. I am sure you will enjoy your 6DMKII