Post-Union Viper build

Why would i not just get dash and bullet time immediately after 1 somersault?
Up to you. 1st job is pretty fast as it is, and the build won't really matter too much, but dash takes up a crapload of MP at lower levels. If bullet time gave speed instead of just increasing your speed cap, then I may see the logic in your point, but otherwise it's not as important as sskick.
How is mastery not as important as mental clarity AND pirate training AND tornado upper?
Mastery used to be really important, but it's just meh now. If you really want to change it I'd put mastery between clarity and training, I just put training early so people wouldn't have to add dex for equips. And tornado upper is pretty goddamn weak, tbh. It doesn't get much stronger with levels.
Higher than 10 SI is still laughably unnecessary, time leap should be maxed before viperisation imo (19x? What the f'uck are you thinking?), i would still do MW and warship over dragon strike, and i guess that's about it.
I still find almost no use for Time Leap because all it does is help dice rolls. YOU may have a better use for it, but I don't. And since you said mastery is so crucial, why would you delay Viperisation any longer by putting time leap in front of it? And yeah, MW is probably better before dragon strike, but leveling via PQs usually meant that someone had at least 19 MW at all times. I wouldn't put warship before it, though. We don't have LHC, so warship's a completely garbage skill.

Thanks for the guide. This will come in handy for redistributing my SP.

Why energy blast before dragon strike?

As takebacker said, it's just a filler in between when you don't have energy. Energy blast does crazy crazy damage.