Our guild just did Nythendra and Il’gynoth tonight (logs here if you want them)
I found Deluge+High Tide a waste since it was eating my mana, and we started to spread a bit more, due to being so many people and the Rot debuff.
Instead I went with Torrent, AG, Vigor, Cloudburst and Wellspring, which actually turned out great. I did try to game Cloudburst with Wellspring/Gift of Queen/AG(make totem pop before AG expires to doubledip) to make it hit hard.
Also, dunno if your raid requires WRT, but I found Graceful Spirit really good for moving out of Breaths. Thinking back tho, I actually want to try out Gust of Wind on the fight, seeing as you can use it to quickly get out of breath, stand around and heal for a bit, and use it to move back again. But if you have good amount of immobile classes, and not enough Stampede, WRT is really useful for the Breaths.
On Ilgynoth I went with a “dungeon-spec” in the form of Undulation, Crashing Waves, Vigor, Echo and Ascendance, seeing as there is not much raidwide dmg going on, apart from the explosions inside the eye. Went with Gust on this one, to save my ass, when dropping the last explosion in the back side of the room, needing to get out before it closes. WRT is also very nice for this, seeing as you only need to get out of there once.
Sry for the wall of text, hope something useful is to be found in there ! 😀