Crit BiS
Prerequisite:
Garuda-egi
1 stack Aetherflow (with Aetherflow off the cooldown)
HQ Deviled Eggs for Coil
HQ Buttons for Extreme Primals
HQ Mega-potion of Int
HQ Potent Poisoning Potion (optional)

Opening Rotation: – (skills in parenthesis are off the global cooldown)
( Raging Strikes ) Bio II >> Miasma >> Bio > ( Fester ) > Ruin II + Move to CLOSE RANGE >> Miasma II > [optional] HQ Poison Pot >> ( Swiftcast ) Shadow Flare + Contagion >> ( Rouse ) > Ruin II >> ( Spur ) > Ruin II >> ( Fester ) > Ruin > [varies in fights, read below] ( Enkindle )

Why use Miasma before Bio II??
- Miasma applies a slow, and it is crucial in some fights like Dreadknight to apply a slow immediately. Other than that, it is all the same.

Shadow Flare:
It doesn't matter if there is only one monster. Use Shadow Flare every time. Think of it as an extra DoT, so keep refreshing it. Pre-cast it on places where monsters will be.

What makes you a pro summoner is the ability to do the opening rotation correctly, when to use Enkindle, and of course.. to know when to clip your dots.

Lesson 1: Opening Rotation
Make sure to cast TWO Fester for each Raging Strikes
Use Miasma II every time Contagion is ready. Miasma II requires you to move in, so make sure to use Ruin II while moving. Never use Miasma II if Contagion is not ready since it's a waste of MP.
HQ PPP is optional, but it gives you a DPS boost.
Weave in Off-the-GCD skills always and use it with Ruin II

Lesson 2: When to use Enkindle
Always use Enkindle with Spur and Rouse pet buff up. Enkindle has a 300s cooldown but hits like a truck and is an AOE, so it is imperative to use it at the right time at certain fights:
Twintania: Use it in your opening rotation to kill Drakes faster, and use it again during Snake phase right after using LB, then use it off cooldown.
Ifrit EX: Use it in your opening rotation, then again during the last nail phase. Use it where there are two nails beside each other (also Bane there).
Titan EX normal-speed: Use it in your opening rotation and then again when first set of adds are up (also Bane there).
Titan EX Speedkill: Save it until add phase. Use Bane and then Enkindle.
Garuda EX: Use in your opening rotation, and again for plumes phase (don't hit Spiny).
Coil T1-T4: Use if off cooldown.

Lesson 3: When to clip your dots
By "clip your dots", I mean 'refreshing the dots before the timer runs out'. The right time to do it is when your DoTs are about to go below 12 seconds, and when (in 6-7 seconds):
The monster is about to "jump", for example: Titan. After doing the fight countless times, you will notice the exact times that he will jump – depends on group DPS, but you will know the HP % by then.
You know that you might be "frozen", for example: (i) Twintania Conflagrations, and (ii) Titan Gaols.

Extra Lesson: Festers and Bane and Pet
Please, for the love of Eorzea, never use Energy Drain over Fester in any circumstance. You might run out of MP, but that's why Aetherflow gives you MP back. The only time you can use Energy Drain is when Fester is down, and you wanted to Ruin II + Energy Drain combo a monster to get the killing blow.

Bane:
The function of this skill is self-explanatory, but the right time to use it is tricky. Whenever you want to Bane, make sure that the DoTs are Contagioned. Best times to use Bane:

Twintania:
Use on the Drake Adds right after you put all 3 DoTs with Raging strikes buff up, and use it again on a contagioned Number 2 Drake Add to reapply the DoTs.
Use on Conflagrations (manage aetherflow stack well here), Snakes, and Dreadknights (but reapply Miasma to slow it).
Ifrit EX:
Use on the nails that spawn right next to Ifrit.
Last nail phase: Use on the nails that are next to each other.
Titan EX Speedkill:
Use on gaols that the BLM is unable to do Double-Flare with.
Garuda EX:
Never Bane the Spiny Plume.
Use Bane when Garuda and a sister are right next to each other.

Which Pet to use and how to micromanage it:
Garuda-egi all the way, and Contagion + Miasma II every minute.
Make a macro with ALL your skills to add:
/pac "Wind Blade" <t>
Have your "Obey" skill on an easily-accessed button. I have mine on "F".
Position Garuda-egi where there is less chance that she will get knocked back.
In some cases like Ifrit AOE Pushback and Titan Landslide, you will have to manual move Garuda back in range for DPS. Otherwise, it will only sit there idling. The easy fix for this is to spam your "Obey" skill on the monster as it will go into range by itself.
Whenever you want to Enkindle or Contagion, make sure that Garuda-egi is on "obey" on the monster you want to use the skill on.

Credits goes to Artemis

source http://shinra.guildwork.com/forum/th...ow-to-summoner