Considering the amount of effort one has to put in for IS, I have to say, without offense to anyone, that it ain't worth it. Level 2 crests and 4 boxes of blue/red crystal ain't worth the effort. Watch that video this guy opens 20 Infernal Chest and not a single revite -- mostly just junk crests you don't need. Honestly it's a catch 22. I'm pretty sure top players who can beat it don't need those crests and those who really need them can't beat it. It's like 2 years ago no one wants to do Lava1 because rewards are not as good as Mesa 4. IS is more of a thing for people who's maxed out all their heros and just like to be challenged.
Lava3 is way more exciting. Yeah, many ways to do it but you get way better rewards than some crystals that I have plenty of.