The botanist is a fight with moderate raid damage that goes up as the fight goes on. The first ability you have to check out is Solar collapse as it can be dodged but you have to be ready to eventually throw a Vivify on people that didn’t dodge correctly. The first raid-wide AoE damage is Controlled chaos, it will pulse 3 times with a delay of 4 seconds between each explosion, even though the radius grows with each pulse the damage remain the same. The second raid-wide AoE is Plasma kek, the boss will start casting it from p2, the boss will summon 3 spheres and once they die they will explode dealing damage, there will always be 3 explosions. The boss also applies Recursive with his melee attacks which means that both tank will take regular damage throughout the fight.
I recommend that you use Chi-Ji and Revival (and Perfectly Preserved Cake if you have it) on Controlled chaos and Plasma kek but obviously not both at the same time, their damage won’t change throughout the fight so you should use them as soon and as much as possible.
The boss will also target a ranged with Fetters so be ready to Detox him, but you should wait at least 1 or 2 second to give some time to your other ranged to move away from him so they won’t get instantly jumped on by the two lashers you set free.
For this fight Healing Elixirs is overall a great survival tool but Diffuse allow you to survive more easily if you walk into Spore or can offer great surviviability on one particular event if you time right. You’re trading off more general surviviability for a trump card during some specific events.
You can actively contribute to the control of lashers here, if there isn’t already a shaman/hunter that can stun at ranged you should talent into LEgsweep so you can stun the lashers when they spawn, but be careful as if you’re fixated you’ll get jumped on when going in for the stun, you should wait a bit to see if they fixated on you or not.
Else RoP makes an excellent job at keeping the lashers at bay, but be sure to not cast directly on the lashers as it’ll bump them all over the place but rather cast it on the melees or the ranged being targeted, and tell him to stay in the RoP.
On this fight the ranged won’t be at melee but there won’t be a single pack of ranged either, you should still try to get the most ranged in your CB as you aim for the melee clump to get the most healing out of it.
In Mythic all three personalities of Tel’arn will be there from the pull, so every ability is present at the pull, the difference is now their HP are not linked and you have to chose in what order you kill each personality. The usual strategy imply killing the naturalist first and then the arcanist before the last one, as a result several abilities will be modified.
When Naturalist dies Spheres will summon 2 lashers so be ready to control them.
When arcanist dies dispelling the Fetter will result in a and only the tank and people 4yards around him will get the Fetter so the point is to never dispell the tank and keeping him alive through the ramping up DoT damage. After 1/ min the DoT will start to destroy your tank requiring a lot of attention, but the boss will still cast Spheres (they do not spawn lashers).
There is different ways to tackle this part as a MW :
You can spec into Mistwrap and fully focus on tank with Envm + SooM and assisting the raid with Chi burst and some TFT-Vivifies
You can spec into Lifecycles and assist more on the raid damage without completely giving up on the tank, you can even further focus your healing on the raid by using some EF to heal the burst damage from the spheres and thus healing your tank even less.
You will only get one cast of Cocoon so be sure to use it as late as possible when the damage is the highest on the tank, remember that it will also apply Envm so try to use it when your mist is in pandemic range.
You can now use Revival without dispelling the tank so feel free to use it when needed.
During this phase people with Call of night will usually be suicided and then ressed, be sure to not waste any mana healing them.