Benthic Typhoon you should have already used prior to beginning the solo skillchain, to increase the damage of both your Chant du Cygne and the spell used to close Darkness. Personally speaking though, I've found Amorphic Spikes to be better for multiple reasons
1) It tends to do more damage. Even though I've had some high numbers with Benthic in the past, I've found Amorphic to consistently do better in the same circumstances.
2) It's multi-hit. One of the problems I have with using a single-hit spell to close a skillchain is that it's an all or nothing skillchain. If the spell misses, then the skillchain is ruined, and you've lost a good chunk of damage in the process. With a multi-hit spell, unless every single hit missed (which would be unlikely unless you were fighting something with insane evasion), you're still going to form a skillchain, and thus get at least some of the damage you're looking for.
3) Benthic is a line-of-sight AoE attack. If there's another mob in range that's in that direct line, you may tag it with the Benthic as well, and thus inadvertently get yourself killed by having another mob on you you're not prepared for.
Lady Jinte wrote:
Vlorsutes' Negotiation Skill rises 0.2 points
Vlorsutes' Observant Parent Skill rises 0.3 points
Vlorsutes' Argument Diffusing Skill rises 0.1 points