Hearthpwn

For me I have noticed that my ideal MMR range is 5500-6000 MMR. I enjoy pushing up the tiers and trying for fun late game builds and once I hit 6k ot above the gameplay I enjoy drastically changes and becomes less fun. 

What MMR does the game become unfun for you? 

How do you check this?

I don't know if there is another way but I just know what rank I currently am at and typically have played at over the past year and use that as my baseline. I have never reached 8k mmr but have spent a fair bit of time between 6500 and 7500 mmr. I found that I had the most fun playing at the 5500-6000 mmr ranking compared to the 6001 and up rankings. 

To me the pool levels seem pretty drastic.  I've been playing between 6k-6.7k for a while now.  After a bad streak I fall back towards the floor and then opponent skill drops significantly and I can enjoy it.  But if I go on a good streak my opponent pool seems to significantly increase and I have a much tougher go and usually fall back quickly.

At any level with crazy high rolling... The highest I have been is 8,700. Greedy OP heroes that don't get punished for fast leveling ruin the game on turns 7-9 where they can one shot you for the most part. This ruins the fun completely