Good way to look at how difficult areas are is by looking at what strategies can been deemed the "best" ones.

In FSC, shivermist + blitz is the way to go. You see this challenge being upped in the shadow lair version, where Darkfire Vanaduke is immune to shivermist. In Tortodrones, the meta really is use normal damage gun charge attacks, or alternatively blitz the tortodrones asap.

Grinchlin Assault last arena? Literally the way to go about it is to die in front of the battlepod and spark up then blitz the battlepod. It just... Gah when your game makes players think they have to die in order to win it's selling itself short really.
And really all we really need is something small changed in order to make it more friendly. Something like longer respawn times on all enemies, mender having much longer respawn times, rocket puppies being changed to regular gun puppies... It's just a flustercluck of stuff going on and all progress is easily undone by that one respawning mender.

I mean yeah, I have beaten the final arena without sparking, even without losing my ER, but the rest of my team was just going blitzkrieg on the battlepod while I was making sure the mender didn't cause problems. It's just not a fun boss battle.

Tortodrones on the other hand... Despite a bunch of things happening at once that is a fun boss battle. Lots of people ignore the fact that non-normal devilites and the silkwing don't respawn and get killed by overtimers/greavers, but as long as they are taken out your tortodrone fighting will go much smoother.

I could've sworn that tortodrones were immune to all minor statuses... Unless you mean freezing the devilites, which can work.

My typical tactic is to burn the tortodrones and kill all non-respawning fiends ASAP. In the past I'd also spam sun shards to get stun spread around as well but I like to a take on new tactics.