We were finally able to nail down a consistent, reliable strategy after some trial and error.
Tank party: PLDx2 GEOx2 WHM. Mage party: BLMx3 SCH GEOx2.
Reasonings for setup:
-PLD x2 was used because it has wonky hate, similar to Seiryu mechanics, where once damage is dealt to it, it will partial reset hate on its current target and chase the person who damaged it. This can be completely negated by having a 2nd tank who tries to get hate during periods when damage is done to it. Doing this, it did not chase BLM even once the entire fight. This is extremely critical because it heavily favors using Clarsach when someone pulls hate at a distance, usually resulting in the entire backline getting 1shot.
-WHM was pulling hate a lot and wiping the backline, so we ended up having the WHM stand with the tanks.
-BLM x3 was used for Death MB. We elected to Death x3 each skillchain instead of splitting them up. We were still able to do over 15% damage per skillchain(260K damage) with 11 characters.
-GEOs were used for vex/attunement/focus/wilt and entrust haste cycle for tank party, which made Teles very manageable to deal with. Focus was so the GEOs in the tank party could land dispel. GEOs in the mage party did standard mage GEO buffs/debuffs.
General fight information:
SPs:
-Uses SPs in random order at 79, 59, 39, 29, 19 and 9%. At 9% it will keep using SPs over and over.
-Each SP comes with a mega range aura.
-Soul voice: 1 minute silence aura and it gains access to virelai and a charm TP move called Entice. Vex/attunement will block Entice 99% of the time, but only charm buffer can block virelai reliably. Important to note that charm buffer can be dispelled easily in this fight. We had PLD use Sent. or invincible when this aura was up, but tank party will still have to rely on healing temps if HP goes too low.
-Manafont: 1 minute MDB down aura. Laughably easy to deal with if you have vex/attunement and Aegis on PLD. This is a good period to do as much damage as you possibly can.
-Invincible: 30 second 200-300/tic dia aura. Manawall can block this damage, which leaves the rest of the mage party to heal themselves. As long as no one panics and uses cures/temps, it's not too bad to deal with.
-The biggest part of this fight is the ability to deal with and survive these SPs. Once a group has this down to a science, the fight feels a lot less difficult.
-It's VERY important that you do NOT push it down below 10% until you're completely ready. At 9% it will go into SP spam mode, making it a nightmare to deal with. We discovered that we could push it as close to 10% as possible, then do a volley of 3 Deaths at the same time to entirely ignore the shitfest that is <9%. Before we figured this out, we had at least 5 wipes ranging from 3 to 8%.
Random stuff:
-It's very important to pop this at a spot where the mage party can abuse terrain due to Clarsach's range. There are a few spots that work, but we settled on the spot near warp #2.
-We never saw it cast Death even once out of numerous attempts. All I can think is that white procing it semi-annually(dark or ice damage seem to proc white often) prevents it from casting Death.
-I'm still not positive what type of damage Clarsach is, but it seems likely that it's wind magic. Vex/Attunement/Baraero seem to drastically reduce its damage, but can still see high spikes of 1-2K or more.
-Clarsach gives it many buffs, including Attack/MAB/MDB/Meva boosts, so it's a good idea to have several people on Dispel duty.
-Miso ramen is the food of choice for the tank party. Meva/HP and defense, all very important in this fight.
-Title: Teles Terrifier.
