I was able to access bitcoin.miningpoolhub.com last night (about 12 hrs ago) using https.
Right now I tried and cannot access bitcoin using either http or https.

However I was able to access aricoin, checkcoin and dash during the same time.

I then waited a few minutes and tried again and bitcoin worked, so it's very sporadic.

I did notice that the bitcoin page always takes longer to load than some on the other coins.  Perhaps it's a load issue and Cloudflare isn't waiting long enough for the page to load before reporting a time out?