Some advice I caught from Fox in region chat:
Fox: use the 2 ability when the boss is at about 30 mana. then youll have thorncoat for the boss' hurty ability
Fox: also use block when boss has 50 mana

And words from Krin in gen chat:
Krinadon: [15:50] Lol. With this - the goal was to have the boss be beatable, but require some high end pets and high end LG gear. So that's mostly be on par so far with the amount of players who've knocked it out
Krinadon: [15:51] More will get it down after they practice it a bit. And who knows, I might knock the difficulty down a bit more at some point
Krinadon: [15:51] Atm though, I want players to feel that sense of accomplishment for beating a very challenging, albeit relatively simple, encounter

Also, if anyone is interested, I am renting out the team I used when I became the first person to defeat the new boss. The waiting list is growing fast though ^.^;

Also worth noting is that this boss is a one-time kill. Once you defeat it, it will not respawn. :(

Edit again to add:
Bananafood: [16:27] I used a shadow/water/light team
Krin had specifically recommended a tank-healer-cannon team OR "an all support team for better survival".

Stats!

ty for the thread, I was able to pm som and get the map

Thus far this is what I have found from a deliberate fight to get his data clearer. I'll update this as I go along, though other's input will help build his profile faster.

1. Vardune, Storm's Fury's, Lightning Arc 240 - 1,506; Multi-Attack.
*** Afflicts whole party with Singe 1,500 - 2,000 Magical Damage for 3 Turns.
2. Vardune, Storm's Fury's, Lightning Slash 1,340 - 1,460 Physical Damage; Single Attack. +10 Mana.
3. Vardune, Storm's Fury's, Lightning Storm 2,374 - 2,819 At 50 Mana / 100% when blocked. Half with Ice Barrier. Only used at 50 Mana (100%).

Turns are consistent, Mana build-up isn't:
Turn 1: Vardune, Lightning Arc Multi-hits for Magical Damage! Afflicts with Singe!
Turn 2: Vardune, Lightning Slash One-hits for Physical Damage! Plus Singe damage.
Turn 3: Vardune, Lightning Slash One-hits for Physical Damage! Plus Singe damage.
Turn 4: Vardune, Lightning Slash One-hits for Physical Damage!
Turn 5: Vardune, Lightning Slash One-hits for Physical Damage! 100% Mana
Turn 6: Vardune, Lightning Storm Multi-hits for Magical Damage! 0% Mana
*Cycle Repeats*

Mana Build: First turn is +20, followed by +0, Then next five turns of mana build-up +10 (excluding turns where mana drains to 0), then another +20 turn followed by +0 mana... Effectively, this is the order of mana growth that makes the +20 boost appear random.
Ex: +20, +0, +10, +10, +10, 0%, +10, +10, +20, +0, +10, 0%, +10, +10, +10, +10, +0, +10, 0%,..
As you can see, that last +20 changed. If it goes over 50, the Mana Build will replace the +20 with .., +0, +10 to achieve 100% mana for attack.

Tactical Notes
1. Verdune only needs 50 Mana to max. out, so limit or avoid using abilities costing more than 50 mana to prevent mana drain.
2. Critical Negation is important, only provided by Earth's Thorncoat & Water's Ice Barrier; Ice Sphere too but too Mana costly to use too often.
3. Taunting to control where Lightning Storm & Lightning Arc strike is essential for success. Both Earth & Shadow can do this with key #3, but shadow has no critical negation ability.
3. Jaidi's Skermishing Technique, key #1 & 2 only, likely best option.
4. Lenore wins the day here, Earth, Water, Light team for non-max. stat team success. Shadow, Water, Light might work too.
5. Pay attention to elixirs for Mana instead of health.

Strategic Success: Again Lenore and Jaidi deserve more credit than I but here goes.
Turn 1: Earth: Thorncoat, Water: Ice Sphere (only time it may get used), Light: Key #1 or #2 attack.

Turns 2-4: Generally use attack keys #1 & #2 thoughtfully. Try to maintain Thorncoat and Ice Barrier on the Earth tank as soon as they drop; This is my advice for 0% - 80% Mana. Also, expect to activate an elixir every other turn in order to keep your party's mana up. Water & Light abilities will make up the health healing.

Turn 5: Vardune @ 80% Mana. Earth: Key #3 if not already taunted to reduce it hitting multiple targets at 100% Mana.

At 100% Mana, Block with all three, although Taunt usually assigns it ALL to your Earth tank, I noticed a few stray strikes on my cannons; odd I know,

just so you know, Agility is itself what controls Evasion chance. Like how it's Agi and Str that affect Phys mitigation and how Agi and Int do Magical mitigation, it's both Dex and Agi are used to calculate a pet's speed in battle.
Quickness rating is (Dex+Agi)/10 (with -0.05 on pets at least), so far as I can tell
Take my main tank, who has Dex: 333 Agi: 1,176.
(Dex+Agi)/10-0.05
=
(333+1176) = 1509
/10 = 150.9
-0.05 = 150.85

Hence why this bos has 150 Quickness. 1000 dex + 500 agi = 1500, /10 = 150.0

Can't help ya here much, harley. I killed it without much thought. it just did high amounts of damage and that's about it. critical damage immunity and taunts were key. and maybe some double or triple water team would be a fun way to laugh off the aoe damage it does.

Wasn't seeking help Jai, it's all about the adventure and overcoming the challenge for me!

But since folks will be looking for thoughts on how to deal with this guy, I think this'll be the best place to post all of that.

okay, please avoid pinging me in the future then. I was going to ask why I was pinged and saw this,"though other's input will help build his profile faster."

Wait a minute, you pinged me!