Coquille 15 is IMO very important, cuz u can armor break for a longer duration than on lower lvls (basicly u dont have to refresh that debuff as often, which boosts ur overall DPS cuz u can spam ur DPS Skills more)
Composee 1 is mainly for the SP consumption, i did tests with lvl 10 Composee and it was horrible - u run out of SP very fast, and than ur dmg is screwed…
So my advice for every Fencer is Coquille 15 and Composee 1
(include Venier +2 Skills u have Composee 3, which is okish)
Increasing Composees Skill lvl also doesnt make that big of a difference (For sure ur dmg would be higher with a higher skill lvl, cuz the Skill Atk gets multiplied by everything, but u can´t spam it 24/7)
For my part in ET i couldn´t keep up with Sp pots in Boss Fights, on the DPS Floors also u have to fight for ~3-4 minutes without a break and than ur Dmg would be too low, cuz of SP problems.
Keistas Potion might do the trick, but - yeah we dont have 100000000 of those