Hunters: Grab a Sword, and a good pair of Daggers and Saber. Use the Dagger/Saber on the Darvant-like creatures. Save the Sword for when De Rol gets on the raft. When De Rol Le is swimming on the sides, use a Handgun, but don't expect all 3 hits to connect. After taking 10-15 minutes to defeat the bastard, think about this: Rangers and Forces don't have the advantage of hitting De Rol Le in multiple places...in Normal Mode.

Rangers: Grab a good Rifle and Handgun. You're in for the long run. Just shoot whenever De Rol is open, and fire away. Dodge like a madman...or woman. Inbetween his laser attacks, fire off a 3-hit combo. (Hunters should also be doing this in every mode after Normal Mode.)

Forces: Gifoie is a MUST. That's all you're going to need. If you get Rafoie, don't use it. It's not worth wasting all of that TP. The trick here is timing: you have to find a good point where De Rol Le is vulnerable long enough for Gifoie to reach it. When De Rol is on the raft, just launch Gifoie like crazy...and carefully. Use Foie when he's on the sides, and Zonde when he's either behind or in front of the raft. You'll have to conserve your Monofluids wisely (in fact, save any Difluids you find in the field...don't feed your Mag with them.)

Hard/Very Hard Strategy:
Hunters: Same as before.

Rangers: Use that Partisan! Shots are rather slow here, and it only hits 5 spots. I'm sure you can hit more with a Partisan.

Forces: Gifoie again and again. Or use Rafoie.

Ultimate Mode Strategy:
Hunters/Rangers: Same as before.

Kinda tough with certain points. De Rol will toss out purple mushes of energy right at you, and it's kinda tough to figure out where to go since he'll toss out another wave when you have it figured out. Sometimes it's best to stay in the corners.

To deal with the Darvant-like spikes, simply pick a corner, and destroy the nearest one. Stay as far in the corner as possible. If you have to deal with 3 of them spinning around you, you won't be powerful enough to destroy all 3 in Normal Mode. Just get rid of two and pray the third one won't kill you.

When De Rol Le gets up on the raft, you have the opportunity to pull off any physical attack combo twice and then you have to start running from the tentacles. As soon as the first one lands, hit De Rol with one combo and run away. The next tentacle will come. Attack. Run. Attack. Run. Attack. If you didn't catch that, he attacks with his tentacles 4 times before returning to land.

De Rol will sometimes crawl quickly on the ceiling and drop debris on you. I'd stick to the southwest corner of the raft to stay alive. Sometimes I get hit, but it's a bit rare to get hit anyhow.

The last attack involves De Rol shooting a laser at you. Stay on one side of the raft, wait a second, then head to the other side. I think he shoots 4 or 5 times.

Ultimate Defensive Strategy:
Dal Ra Lie was given some sort of pep pills! He's a crazy one! His attacks kind of follow a pattern, but they are randomized too! He'll always launch those purple orbs at the beginning of every fight, so get used to it!
When he's on the raft, his tentacles will attack much faster! You could probably only get in weak-weak attacks and run away. Learn to dodge close to him so that as soon as the tentacle is about to land, you're whaling on 'im. Oh, and he'll also get on the raft when the lights are out. Expect more attacks when he's cut the lights.
Lastly, his laser beam attacks are unpredictable! You are guaranteed to get hit at least twice!