As for the emergent skills (lvl 65 and 70 subclass skills), I think it is wise to go with ONE option and choose it all the time, even for future additional subclasses (so that in the end you have 6 times the same passive skill). For example, one time choosing pdef passive does not add much, choosing it 6 times is a nice pdef bonus. For a SE, I would go for either pdef or mdef - but in the end that depends on your playstyle, maybe you would like a patk boost instead. As for the 75 skill - during the event, you can choose a 75 skill from ANY class, not only from the subclass you actually have. A clannie has the UD skill, it adds (he says) about 300-400 pdef and mdef when it triggers (chance when you get hit), that one seems pretty nice. I have gone for the barrier skill (5s celestial shield) and the chance haste (+30% attack speed) since I do attack mobs when I party on my SE. If I had the spare money to redo it all, I'd probably go for UD and chance haste instead (UD lasts longer than barrier and you can get healed). But it all really depends on your playstyle, just look at the skills and choose something which is useful for you.
As for the emergent skills (lvl 65 and 70 subclass skills),
I think it is wise to go with ONE option and choose it all the time, even for future additional subclasses
That's a wise idea, i think i will go for pdef indeed all the way.
As for the 75 skill - during the event, you can choose a 75 skill from ANY class
I dont think I will make it to 75 before May 20th.. And my sub is a Rogue (HE), so choices are limited.