It's not necessarily about having it memorized, but about not having to move while doing that opener. A lot of pug groups I see force you to stack up for the beginning of Titan extreme (despite the arena being huge at that point). If you place your pet and run in immediately, you will still have to move for landslide/weights while casting your opener spells, and as I said... your way, you only have a few seconds between your last fester and when RS ends... Now, if you really wanted to keep the extended duration on the buffed dots (which yes, technically would be more), another safer method would be to use your normal (non-buffed) Bio II > Miasma > Bio > RS > Fester > SF + Fillers... > Fester > re-up dots > Contagion. The dots that were added after the two festers and will still be buffed by RS, and the only loss would be about 10 seconds on your Contagion cooldown, which you likely won't use EXACTLY when it's ready in movement fights anyway, so the 10 second loss is not too big of a deal.
I'll be honest with you -- I lurk these forums a lot, and a lot of people tweak their rotations slightly compared to others and still pull off 300+ dps with their pet, even without 'best in slot' items... and they do things I and other summoners wouldn't necessarily agree with. There is not 'one way' to do something, or every single high-parsing summoner would do the exact same thing. What we're doing now is theory-crafting, and I'm not saying your idea is wrong... Rather, I am defending mine as not being wrong. But these are seriously just negligible preferences... as I have seen no difference in parses (according to people who actually parse me on fights; I don't parse). This is such a small thing to be arguing about when the point of the thread is to help the OP.
One specific piece of advice I forgot to mention is how to be effective at strong SMN dps on an add that you need to down ASAP (example: rocks and conflag). Make sure you have your dots on the main mob first, then Bane those the second the add pops... and fester on the add. Groups with REALLY good dps won't require you to do this, but more often than not you will be the lifesaver with the instant 1k+ hit.
You have about 2-3 seconds if you wait to *see* Bio before Festering the first time (which I do because otherwise there is a chance you won't get the full damage bonus.. that's the reason I started using RS after Bio in the first place, to save time on the GCD). I play on mouse+keyboard... I don't know why playing on controller would make that harder? I never said it's impossible to pull off two RS festers, but I did say it's harder to pull off IF there is ever a time where you have to move while using it... And that won't always be at the beginning of the fight.
You're all telling me I'm wrong but I'm consistently told I'm outparsing everyone in my party at 300+ dps (plus pet). I don't even parse myself (I think parsers are inherently problematic) or I wouldn't make these claims. People just like to point it out to me. So no, I am not feeling like I am doing something wrong, or at least not something that alters dps by much. I'm going to stop replying to this thread though, because it's getting to the point where it's not helping OP. If OP seriously has damage issues... trust me it is not because of the negligible time at which I am suggesting to pop RS, but they are welcome to follow whoever's advice they like.