I've recently discovered Fang Dive (D Skill) is also a good skill to max.
The % isn't as high as other skills, but the cooldown is significantly lower, and there was a gigantic piece of information that wasn't translated until recently:
Upon getting the Master cube for the skill (level 10), you will get back 1% of your Phase Gauge PER HIT.
So Fang Dive is a very good option to max.
If you're having a difficult time choosing what to max (since I'm giving you like 4 skills to max now lol), this is order in DPS (based on cooldown and max hit damage; highest first, lowest last):
- Fang Dive (D)
- Serpent Swarm (E)
- Designated Flight (Q)
- Tail Whip (S)
You can actually max almost all of those right now at lv58, since OC isn't out yet.
Also, I apologize for giving you the wrong key for Tail Whip, I don't use the default keys x_x;
As for the reason why Serpent Swam is now ranked up higher than before, well...there was an important piece of information that wasn't translated for that, either: It has 50% Magical Defense Penetration at Master level
It's also very good for stalling cooldown.
When Official Crew comes out, and in the occasion you ever run low on SP, the skills that I would say are MANDATORY to max are Dimensional Singularity and Fang Dive so you never run out of mana and have good DPS.
If you have spare SP after that, THEN you could pick to pick one between maxing Serpent Swarm/Designated Flight/Tail Whip.
Personally, I would only max Serpent Swarm since Designated Flight/Tail Whip have i-frame and drain your mana too quickly if you max. :/
By the way, there's a pretty good chance naddic is going to adjust several multipliers when Official Crew comes out, so this information may become invalid when Official Crew Levia comes out.
I will edit this with what is still valid and what is still invalid once OC comes out.