How to Dragoon per Second: A DPS Paradigm

[Aquaslash]

I have tried and tried and tried some more, and I have never been able to skip lapis. Closest I've been is 62%. For the drg player, do you basically use your standard opener and then save ogcds at optical sights to have another opener ready after limit cut? Or do you just need to go ham the whole time?

Also, any tips for a good opener on Scathach? I'd like to not take a vuln stack, but I'd also like to not lose a buffed GK or botd in general

[Sentinillia]

I have tried and tried and tried some more, and I have never been able to skip lapis. Closest I've been is 62%. For the drg player, do you basically use your standard opener and then save ogcds at optical sights to have another opener ready after limit cut? Or do you just need to go ham the whole time?

It's very much a team effort.

What you have to realize as well is that timings and RNG plays a big part in it. To increase your success chances you want to have the boss as much below 70% after the first phase as possible. To achieve this the boss has to be pushed below 72% while he's busy doing an ability, in this case Optical Sight. This is the RNG part as getting the Shiva pattern is a lot better for your DPS than the other pattern.
After Limit Cut you have to push the boss to as close to 60% as possible before he takes off. The options here are to either:

A) Have high enough DPS to push it straight off the bat
B) Have low enogh DPS to not skip the Left/Right Sword to get a few more precious GCDs

After CC lands everyone still has a chance to hit 1 GCD + 1 OGCd before the boss becomes invulnerable. Limit Break 1 can and should be used here if you wouldn't skip otherwise, don't worry about the LB hitting invulnerability as it will go through as long as you start the cast immediately after the boss becomes targetable. If you manage to push the boss to 60.9% he'll become vulnerable again right after he finishes casting Limit Cut and commence Eternal Darkness.

For the dragoon this doesn't change much other than the fact that you really want to have BotD up as soon as the pre-airship phase starts, as well as having it up again right after you land. You also might want to hold your OGCDs during the pre-ship phase.
You can get in two Leg Sweeps, one Jump, two Geirskoguls, and a Spineshatter and DFD depending on your DPS on the first phase. It is optimal to land as many of these as possible inside Trick Attack/Hypercharge. What I've done to solve the BotD conundrum is doing the 4 GK/70s rotation for the first phase, delaying the last GK until the boss starts casting Limit Cut and blowing my BotD there (althought you might be able to get more GKs in if your DPS is significantly lower).
During the numbered Limit Cut I do HT -> ID -> Botd -> Dis -> CT -> (boss becomes vulnerable here) B4b -> 4th -> Phleb.
This BotD timing allows full GK usage in the first phase, gets you into the pre-ship phase with BotD, Disembowel and CT already applied which allows you to spam TTT combo and weave OGCDs for the whole phase AND have BotD up again before Eternal Darkness.