I did this quest yesterday. Failed at it twice, both times shortly after adds came. So I came up with a new game plan, and here is how it went down:
-I went to the market board and bought a few X-Potions, a Stronger Paralyze potion, and a STR potion (never did use it, not sure if any potion use trigger the 5min GCD...or if when I bought it it had a GCD and I just didn't pay attention.)
-I had lv8 CNJ's protect and heal, and what I thought was useful lv15 MRD skills.
-Started the fight and moved down into the corner and proceeded to stab away, avoiding his Heart Stopper, and ether Flanking him, or just continuing the basic combo T>V>F.
-Also tried to keep the 2 DoTs I had (the LNC skill, and the MRD's one).
-When he began to do the Ice Rings, I moved out of AE and used Piercing Talon.
-When add's came, I used one of the Paralyze potions on him and proceeded to burn down adds while stay out of Ice Rings, and kiting Foulques. Once adds where done, back to Foulques.
-Used Cure and X-potions as needed. Towards the end of the fight I was basically just using Piercing Talon twice, he would get in range to do Ice Ring, I'd run out while throwing one, cast cure 1 to 2 times, and then throw again as he came at me.
-Paralyze potion did proc a few times and stopped a few Ice Rings and Heart Stoppers (I also used the LNC Stun as well).