Great save!
A few tips and tricks from my experience getting platinum completely solo using this save.
The hardest part are the Insane challenge trophies (in order of difficulty, imo) Treasure Hunter, Zippy Terror, and Ogre Crush. The other insane challenges are beaten with easy builds and some huntress management.
- Treasure Hunter you need bouncing blockades and bowling turrets at pretty much every ramp leading up to the crystals. Spend the first couple of rounds avoiding the gold mana and upgrading your towers to 3-stars. Enemies spawn endlessly but don't get stronger as each round goes on. Equip the huntress with the imp familiar Alocar(?) There's one in the tavern by the shop keeper. He heals your defenses way faster than you could ever do so manually and mana is never in short supply here. The last round or two can get pretty hairy especially if a tower falls.
- Zippy Terror. Equip the Laser Robot familiar on the huntress and the piercing weapon that's in the item box. It's black and fires blue swirls through walls. Being able to fire without line of sight makes this sooooo much easier. Stand close to the west crystal but look east for kobolds first.
- Ogre Crush. Piercing weapon on huntress, harpoon towers, and a quick reaction time. The ogres can hit your crystal from pretty far.
Team Effort can be achieved with one controller. From the start-up screen, select local play, choose a hero with P1, then
before hitting start, switch the controller to the other three ports selecting heroes as you go, then switch the controller back to P1. Hit start to head to the tavern. Choose an easy map on at least medium and start. You will have to wait two minutes between the build and combat phases as
you can't pause or enter the XMB. Doing either will cause the other three "players" to pause, which means you'd be in an endless loop of pausing, so you have to start over from the start-up screen.
The easiest three story levels to do on Insane are Deeper Wells (C1), Hall of Court (C2), and Ramparts (C3).
The easiest level to do the survival 20 on, in my opinion, is Alchemical Lab. [Deeper Wells forces you to split your defense and attention making repairing harder; Insane 10 it's not so bad though] Harpoons pointed at all four ramps, a bouncer guarding the stairs to the ledge to the west, four slice-and-dices around the crystal, a bouncer just east of the crystal (forming a wall* with the s&d's), bouncers on each of the east ramps, and a strength drain and snare aura covering both ramps as well. You can pretty much just stand in front of the wall, with a piercing huntress weapon, an imp, face east, and hold R2 forever. Hit L1 occasionally to make sure Dark Elf Mages aren't ruining your west bouncer. It's possible to run this using the P2-build-then-leave-game method with minimal huntress action if you were concerned about kill scroll freezing, but be warned, if P1 ever rebuilds a tower using the character that P2 used to build the others, you will get all of the kill messages again. I ran all 20 on hard using the huntress auto-shot without letting it catch up using this build. YMMV *The kobolds attack is a PBAE suicide which especially on higher difficulties, has a sizable range and can hit your crystal even though they did not.