Summoner
You apply your DoTs in order of longest duration to shortest:
Bio II > Miasma > Bio
I would recommend not starting off with Shadow Flare as the boss likely needs to be repositioned, unless you preemptively place it.
Next, you start your Ruin II spam to use off-GCD moves. This includes: Swiftcast, Raging Strikes, Spur, Rouse, Enkindle, Fester, Aetherflow, Bane, Energy Drain.
Bio II > Miasma > Bio > Contagion > Ruin II (Swiftcast) > Shadow Flare > Ruin II (Fester) > Ruin > Ruin > Ruin > Ruin II (Fester)
This is your typical rotation as a SMN. Nothing much changes aside from using Contagion whenever you can. and using Ruin II for Spur, Rouse, and Enkindle when possible. Watch your DoTs. If Bio II and Miasma are at 2-3 seconds of duration, start to cast them again.
Bio II (10s) > Miasma (7s) > Bio (13s, this one was probably already reapplied since it's an instant cast and shorter one) > Ruin > Bio II (7s) > Miasma (4s) > Bio > Ruin II > Begin Miasma's cast > Begin Bio II's cast
If any of your DoTs fall off at any given time, you are playing a SMN wrong. Bio can be reapplied right after it falls off, as our DoTs tick every three seconds. The rest should be preemptively reapplied. No exceptions, if you can help it.
Now, for a buff rotation. I recommend starting every fight with Raging Strikes. This will make your DoTs stronger; Contagion any Raging Strikes DoTs if you can help it and get the most out of them. Spur > Rouse > Enkindle should always be your rotation if you can help it.
As a final note on a SMN's rotation, there is one exception to the Ruin II rule: Bio. I will example it now.
Bio II > Miasma > Bio (1s) > Bio (Fester while on GCD)
Since Bio is an instant cast, this will make it so that you can Fester and then go back to your usual Ruin spam until you have to Fester/reapply again.
Bio II > Miasma > Bio
I would recommend not starting off with Shadow Flare as the boss likely needs to be repositioned, unless you preemptively place it.
Next, you start your Ruin II spam to use off-GCD moves. This includes: Swiftcast, Raging Strikes, Spur, Rouse, Enkindle, Fester, Aetherflow, Bane, Energy Drain.
Bio II > Miasma > Bio > Contagion > Ruin II (Swiftcast) > Shadow Flare > Ruin II (Fester) > Ruin > Ruin > Ruin > Ruin II (Fester)
This is your typical rotation as a SMN. Nothing much changes aside from using Contagion whenever you can. and using Ruin II for Spur, Rouse, and Enkindle when possible. Watch your DoTs. If Bio II and Miasma are at 2-3 seconds of duration, start to cast them again.
Bio II (10s) > Miasma (7s) > Bio (13s, this one was probably already reapplied since it's an instant cast and shorter one) > Ruin > Bio II (7s) > Miasma (4s) > Bio > Ruin II > Begin Miasma's cast > Begin Bio II's cast
If any of your DoTs fall off at any given time, you are playing a SMN wrong. Bio can be reapplied right after it falls off, as our DoTs tick every three seconds. The rest should be preemptively reapplied. No exceptions, if you can help it.
Now, for a buff rotation. I recommend starting every fight with Raging Strikes. This will make your DoTs stronger; Contagion any Raging Strikes DoTs if you can help it and get the most out of them. Spur > Rouse > Enkindle should always be your rotation if you can help it.
As a final note on a SMN's rotation, there is one exception to the Ruin II rule: Bio. I will example it now.
Bio II > Miasma > Bio (1s) > Bio (Fester while on GCD)
Since Bio is an instant cast, this will make it so that you can Fester and then go back to your usual Ruin spam until you have to Fester/reapply again.