Sleep bomb every grave, Hammer everything that comes out, trail of sleep bomb eventually sleeps Harvester repeatedly if you line it up right.
The harvester can be slept, as well as the souls.
You'll have to wait until the scarab attacks fully end before you can start getting near them, but with them sleeping they won't attack again and with most weapons you'll be able to clear them easily, and they don't always wake up after one hit.
If you're playing in a group with some players not knowing so much about how to deal with the harvester, one player could suicide rush the harvester every time it gets close, trigger it's attack but place a sleep bomb right next to them so it won't attack if the player gets captured, and another could just free them, then everyone can run off.
Not being able to rush around attempting to grab souls faster because the Harvester is going after you, sleep bomb usually helps and I'd imagine trailing it as a bait only would be pretty good too if you're not completely 100% confident you'll be able to escape it's attacks if it ever manages to get close to you.

Maskeraith to spook harvester so you can hide every time you get captured with no way out, and a heavy shield in case scarabs are attacking you while you're trying to stealth. Having the harvester near you while you go stealth will show where another player is, if there's a reason you'd want to meet up since it'll go in the direction of them.
Sleep bomb is always fun, regardless.

Have you searched Google (or another search service) for something like "apocrea guide site:forums.spiralknights.com" (without the quotation marks)? That can help a lot.

The Apocrea weapons are not particularly worth getting. So the main purpose of playing Shroud of the Apocrea is the fun of the puzzles. To learn more about them, you might search for something like "apocrea puzzle site:forums.spiralknights.com".

I could solo Shroud of Apocrea with just a maxed Electron Vortex, that's really all you need LOL.