Arachnohphiles are super weak in the beginning. I had a really hard time until I started getting upgrades. I put a flying pilot in the area shifter, then shifted enemies into water and holes. He's useful for pushing enemies in the "kill 4 or fewer" missions. The baby spiders are pretty cool too if you attack weak targets, then you can do chain reactions killing a bunch or use them to block enemy spawning. The ricochet would be good if there was a damage upgrade for it, but at best it's good to push enemies away from targets and into water/holes. They're still my least favorite group so far.
I think this squad is the weakest in the game. They just rely so heavily on enemies being the right position, rather than having strong repositioning options like other squads. The Ricochet is a bigger hindrance than even the Janus cannon. The inability to upgrade the size of the windmill mech makes it so horrendously bad. And the mech that needs to kill for it to get any value only does 1 damage. I suppose this squad will be great for people craving a higher difficulty