Unless I am wrong, Odyn is a world first. I also didn't find a record of a Guarm kill, but anyone with 1.38M dps could have done it.
I was bored of Mythic+, and was wondering why shoot hadn't solo'd Odyn yet. Then boss despawned when I feigned death, and I understood.
Spec used : aspect of the beast build + tenacity pet
Legendaries used : roots of shaladrasil (legs) and apex predator’s claw (ring) for survival and pet damage.
Consumable used : dps flask and rune + bear tartare (speed on kill)
Not a perfect try, but the main point is that he didn’t despawn in phase 3 after feign death, giving me the opportunity to finish him.
Phase 1 :
Prepare a macro to target Hymdall, send your pet to attack him, then target Hyrja. Use it on pull and if your pet targets Hyrja for some reason.
On pull, make sure you are not healing your pet. Use kill command on Hymdall and shoot Hyrja. You must keep them about 35 yards apart to stop them from shielding each other. Try to stay in range of your pet - if you move move than 40 yards from Hymdall, kill command will target Hyrja.
Use disengage to avoid the blade and move as little as possible in order to maximise uptime on legs.
You want to use exhilaration at least once this phase to make sure pet is full health entering phase 2. Use Aspect of the Turtle on the unerring blast.
Once Hyrja is sub 40K, switch to Hymdall until he’s sub 40k, then finish both.
During the transition, put your affair in order - I personally switched unmodified Bestial Wrath and Kill Command with my usual dps/targeting macros.
Phase 2 :
There are 2 notable abilities in this phase.
Odyn’s test will buff Odyn and make him ramp up damage on your pet. Use misdirection at the beginning of the buff, then shell shield once he’s halfway done. Remember to keep healing your pet.
Runes : you want to kill 4 of the 5 adds (3 if using Prydaz). When moving from a rune to another, target the next add to kill and once he’s vulnerable use Kill Command + Beast or Cobra. The buff from the bear tartare will then speed you up.
On the second set of adds, you can either push Odyn to 55% or do the runes. Even if you screw up (like I did) you can use Turtle. This strategy allows you to heal your pet up before phase 3, and get cds back. Just remember to leave some health on the boss so you can keep the AoTB damage reduction active.
Phase 3 :
Other than avoiding avoidable damage, you must manage the stormforged spears. The strategy differs wether you can end the phase in 6 spears (2.41M dps over 77 seconds)) or not.
The main issue is that the boss will DESPAWN 80% of the time you FD (in my experience - your luck may vary). I have analysed feigning death with buffs, debuffs, and certain times, and got nothing - it seems perfectly random to me, so I don’t know what causes this bug.
To have your pet survive the longest, make sure he enters this phase full health.
The best CD rotation is:
Spear 1 : 3M damage
Spear 2 : misdirection = 4M damage. Use exhilaration afterwards.
Spear 3 : Shell shield + Last stand = 4.5M damage. If you use shell shield at the last possible second, it will be up for the next spear.
Spear 4 : Shell shield = 6M damage
Spear 5 : unavoidable death.
If you can achieve the high dps strategy, use the above rotation and for the 6th spear, disengage when he is casting and maybe use AotT, then kill him before 7th spear.
If not, I personally chose to have him kill my pet on 3rd spear. I waited until I had a spear on me then feigned death while praying to the RNG gods. After that, I chained misdirection then last stand and shell shield since I realized I would have only 2 or 3 spears - and even if my pet died, one spear on me was survivable.
Guarm "strategy" : run around to avoid debuffs. Pew pew. Loot.