I've never had a problem with the Jade Scarabs, but I abhorre the Maguuma Spiders. They seem to exist only to annoy. I was able to take on a group of a little over a dozen of them at once with my N/E, using life siphoning spells until I ran out of bodies to draw life from, but put them with any other enemy and they're suddenly twice as dangerous. Couple that with everything spawning from the trees, or the ground, or just a vine hanging a few hundred feet above you and it gets even worse.
I asbolutely hate the entirety of Maguuma for this reason. It's not a truly difficult region, it just takes absolutely forever to get anything done. It's not a test of skill so much as it is patience. Don't believe me? Review Blood and Smoke. I tear my hair out just thinking about the hours you can waste on that mission, just because you get sick of it three fourths of the way through.
Jade Scarabs: WTH?
Plague
Mithie
Okay, I just did it last night with henchies. Much better. I have come to the conclusion that it was the lack of teamwork that wiped out my previous team. It was still sort of challenging, but after a bit of patient pull + focus fire, I got it done. Thanks for the advice folks. Good work henchies. Too bad they never talk.