CC can be very helpful to healers at some points, though Haukke manor was the most I've ever used it. At 50, so far, its not too often used but still helpful.

I know CNJ gets a sleep, I think THM too. Not sure who else.

Shards arent too much of an issue if you dont mind farming them later. Do realize though that farming a few thousand can take an hour or some.

Get one class to 50, then worry about alts. Once you have one max class, you get a +50% EXP bonus to other battle classes to level faster. Level your first through storyline quests and a few fates in between, then level the other classes through fates to level fastest. Only run dungeons when you're sick of fates and want some loot.

Veteran bonuses are received through total time paid for accumulative. The only difference is how soon they are received.
By paying for 90 days at once, you get all rewards the moment you pay.
If you only pay 30 days at a time, you still receive all of the rewards, but not until the time has been paid for. ((I.E., you get the 90 day mount the 3rd time you pay for 30 days)).