So, to clear up some bad information here..

* Raging Strikes does not affect Shadow Flare, and using it before Shadow Flare is downright a waste of the buff
* Prefacing every single off-GCD skill (Rouse, Spur, etc.) with Ruin II is not only a waste of mana, but a loss of DPS. Ruin is practically our worst DPS spell, and you should only be 'weaving' in off-GCD in this way in situations where the fight is either so short that you don't risk running out of mana, or you have something like 2 bards with a perpetual Ballad up, but even then, still probably a waste.
* As mentioned once, Miasma 2 is only worth using against a single target if you are going to employ contagion
* The only way to fit in 2 max potency Festers inside an RS buff is to do RS, Bio2, Miasma, Bio, Fester, Thunder, Ruin, Ruin, Ruin2, Fester or a similar rotation. Fester has to come after the second spell for non-instants or third spell if it is an instant
* The only time you should lead with a Swiftcast->Shadow Flare is generally if you are doing it on the move to reposition. Even though Swiftcast->Shadow Flare goes out immediately, it is not an off-GCD skill, meaning you will still have to wait on GCD to cast again. The best place to fit it in during stand-up DPS is after RS has faded.
* Saving Swiftcast for an emergency is a hedge. If you are in predictable content with a known group, you most likely won't need it. Anywhere you might need to swiftcast a Ress near the beginning of a fight is probably one you are going to lose anyways. I wouldn't hesitate to Swiftcast an early Shadow Flare during evasion/positioning.

During a lot of end-game content, one of the major priorities is focusing on mana and aetherflow management, which are closely tied together. Holding onto Aetherflow charges for too long while Aetherflow is off of cooldown, can often result in running out of mana. If you are not in a position to be able to Fester or Bane, kicking out an Energy Drain so you can Aetherflow again will keep the mana up. You should of course be aiming to utilize all your charges inside the 60 second CD window, but sometime it isn't always possible.

Over-use of Ruin II (such as the example above, using it in combination with _every_ off-GCD ability.. Fester, Rouse, Virus, etc.) is a prime way of running out of mana. Generally speaking, you should avoid using Ruin II except in few situations...

1. Moving while needing to maintain some DPS
2. Fitting extra spells inside a limited buff timer (Potion, RS, etc.)

It is true that weaving spell in with Ruin II will be added DPS, but in longer fights, it comes at a big cost. No matter how much DPS you gain from Ruin II weaving, you will lose so much more if you actually run out of mana or have to fall back on Energy Drain to make up for it.

A lot of maximized potential in the end-game comes from knowing the fights and planning the proper use of your cooldowns ahead of time. Having Contagion available when you are going into an RS rotation, having DoTs up when you know you need to Bane, maximizing Fester output, minimizing Aetherflow sitting un-used while cooled down, utilizing instant spells while re-positioning (not just Ruin II either), etc.

SMN is very strong in end-game content when played well, but can be a disaster if you don't know the content and don't properly maintain a good flow of damage going out. A good performance can be generalized as a fight where you _almost_ ran out of mana, and didn't have to sacrifice DPS to avoid it.