Yes, you could technically get away with speeding through your aether stacks in the very first set of your opener to more quickly get to DWT. In my experience, it isn't worth it. Fester does much more damage to an enemy with both DOTs applied than any of the other three aether skills could net you, and using Fester only gives you more time to evenly spread out weaving your OGCDs in between that and R2 casts. For the opener, you could even double-weave your OGCDs between the two R2s. In raids, I usually like to use Rouse four seconds before the pull, start up R3 at three seconds, and do the above opener I mentioned, with Enkindle > Shadow Flare between the first set of R2 casts and then Aetherpact > potion between the second set. You could have more things to weave through if your pet's on Obey or if you decide to try out the pet-swap opener, but you'll probably end up sticking with Sic-frit in most cases so it's not usually an issue.