Finally got my 8th kill in for King Bememoth.... technically I should kill him four more times (and I may), but as of right now I'm done with this stupid boss, I'll just make the two copies of L99 Behemoth for my thunder deck and deal with it instead of farming the third copy for perfect optimization. I changed my team up some, which made the kill slower, but it's more stable and less reliant on RNG. This setup has zero chance to ever hit mastery, but don't care, I'd rather use 10 mithril on refreshing a daily dungeon for those missing crystals from mastery instead of working on this boss anymore (and saving 50-100 mithril by skipping fest banner 1 makes it worth it).
Here's my final team that worked "best" at farming Behemoth with my available relics:
Onion -- Meltdown r4, Chain Stonega r4 -- mUSB -- +30% Earth RM
Galuf -- Gaia's Rush r4, Protectga r3 -- CSB -- MakoMight
Elarra -- Curada r4, Allegro r3 -- BSB -- Ace Striker
Lenna -- UltraCure r5, Hastega r3 -- USB2 -- DrMogTeaching
Maria -- Chain Stonega r2, Shellga r3 -- BSB -- +30% damage RM -- She has the Major Resist accessory
Magicite:
Midgardsormr (Active), +15% earth damage inherit
Earth Guardian, +10% thunder dampen inherit
Sylph, +6% earth dampen inherit
Gizamaluke, +5% bladeward inherit
Evrae, +15% magic boon inherit
Video:
King Behemoth 1min 4sec (had to remove sound to avoid copywrite strike, I had music playing while farming)
The first two rounds are critical to stabilize the fight and avoid too much wasted hones by damaging before he enrages (and starts taking more). Initial actions are:
Turn1:
Onion -- Wall RW (instant LMR)
Galuf -- Chain (quickcast LMR)
Elarra -- Allegro
Lenna -- Hastega
Maria -- Shellga
Turn2:
Onion -- Meltdown
Galuf -- Protectga
Elarra -- Allegro
Lenna -- USB2
Maria -- ChainStonega
Lenna's USB2 (which applies last stand) should land right after the first reaper and heal everyone to full and apply last stand. I had to legend dive her and max her relevant stats with crystal waters to make sure she lives until this point without heals. From there it's now just a matter of alternating medica's with Elarra and Lenna, both of which have Last Stand (I didn't use Elarra USB at all, needed last stand too much).
It's key to memorize when the savage sunder is going to land (it removes your haste). Time Onion's mUSB to land directly after a savage sunder to get your haste back up. You never have to re-cast Shellga because the only thing it works on is the Thundaga in phase one/two and it won't wear off before phase three. Refresh Protect around the 25 second mark and it should last until the end also.
A tricky point is in phase three when the boss does the savage hurl on slot 5 followed directly by a shockstorm, but if your major resist unit is in slot 5 and you time a ST heal to land in between, they should live. The next hurl -> shockstorm on slot 4 is probably going to kill them, so make sure it's a unit you can afford to lose at the end of the fight.
What a pain in the ass fight.... I haven't even touched Quezcotl, but I guess I'll give him a few tries later tonight even though we don't have stone press yet.