I wish I could like Envy as much as I like hiha, however I feel like hiha is miles better than Envy. They are willing to take their music to places Envy has never dared to touch and that's what give them the edge for me.
I'm glad they're moving into black metal. What an amazing band. I remember a long time ago when Erosion came out someone here said they heard black metal in the sound and I didn't believe it at the time. That said the latest two splits don't seem to have to same quality of their previous releases. I hope they pick it up for the next album cause they're too good to start sounding like that shitty COHOL band.
There are quite a lot post-rock influenced screamo bands these days, but I'll list here a few that you might like: Envy, Sed non satiata, Daitro, Suis la lune, Le pre ou je suis mort, Gantz and June paik just to name a few. You should probably check out Rosetta too even though they're not a screamo/hc band. Best way to find new similar bands is to look what the artist page suggests as similar artists.