I found Insane was much more difficult for earth than it was for water. Snake Spirit is extremely handy, and naga may save your life more than once. Pros will have no difficulty with this, but for the sake of the mid-tiers like myself, I'm going to go into detail below, so if you don't like spoilers, read no further (though as I'm about to post this, I'm realizing hellotik has already put up the values, saving me most of the guilt
). All of the below assumes you're using Achilles, or at least the royal fencer:
The regular satyrs have 5k defense and 50k health, and hit for 1850 damage, and the upgraded ones at round 5 have 10k defense and about 100k health, and hit for 2350 damage apiece. Both types have cd0. Round one you're facing two fairies and a satyr hitting for a total of 4500 per turn, so if you don't have panzers, you will likely need more health than the 7.5k needed for water apoc, plus some immunization/turn buff cards (achilles, princess maria, naga, etc.) to keep you alive until you can kill a fairy or get your shooters primed. Start with one of the fairies, then work the other two down. If you're unsure, I recommend killing one fairy, killing the satyr with your shooters, and leaving the other fairy alive so you can recharge your shooters and then kill her with regular rolls. It can be tough to land enough damage to even break the satyrs' guards, so try to save other enemies to whittle down at the end while your shooters recharge, or you may find yourself using them just to end rounds.
Round two has three satyrs. Regular shooters (Vamp Princess, Succ Queen, Cerberus, etc.) can't kill a satyr in one hit (or at least mine couldn't), due to their 5k defense on 50k health, but you only need to kill one of these to get your safe zone, so double-up your shooters if necessary. Repeat for the second, but on the third, try to hit once and then whittle away the last of its health. Easy with snake spirit, tedious with werewolf, very hard without something capable of ignoring armor. I ended up just spending a shooter and going in a man down for the third round.
Third round, you should have the hang of this. Shoot the fairy (and the satyr if you can), kill the murlock with rolls, kill the satyr if you haven't already, and recharge while killing the second fairy. Easy peezy. You're pros at this by now, you'll have Round 4 down without breaking a sweat.
Bring both shooters charged into Round 5 and get ready to pray. These two bowmen hit for a combined 4.7k every turn and have 10k defense, so you're gonna need damned good rolls to scratch their paint. My Vampire Princess and Succubus Queen got one of them down to about 10-15% health between the two of them, and after that I was mostly out of options. Had to play my survival cards carefully, and for the most part I got lucky. This stage will kill most mid-tier players unless they have SS, a large amount of health (12k+), or some good damage nullifiers (a naga and achilles, for example). Or luck, like myself. The second satyr is easy once you've gotten rid of the first. From there, round six is a lot like round 3. If you actually make it to Pestilence, it's easy cruising. He hits 3.5k per turn, so you can autospin if you're so inclined. And I might add he looks even cooler than his broski, IMHO.
I did this with Royal fencer (only lv12, haven't needed her before), vamp princess, succ queen, naga, werewolf, and HP, for just under 10k health. I'd switch out the werewolf for a SS in a heartbeat if I had one, and I'll be using Achilles as soon as he pops up on my friends list. He should make things much easier, adding health to my party and giving me a third survival skill besides naga and HP. Might even make round 5 consistently survivable, which would be nice since it's the only thing that worries me about running this again. Unfortunately, I find it hard to believe this level is possible without hp beasts, unlike water apocalypse insane. I was excited by the implications of the latter, since it's generally not hard for a player with two 6* shooters and a HP to put together 7.5k health, which, when coupled with a friend's blackbeard, is all you need for a near-guaranteed run. This apocalypse insane was much more difficult for me in a number of ways, and I'm really not far past the cusp that divides those who can beat it from those who can't. My sympathies to all my fellow mid-tier players who haven't been quite as lucky in the shop as I have of late :/