Quote Originally Posted by _Babble_ View Post
One more question on this topic: is it beneficial or maybe even necessary to continue to level my subclass after I hit 15 and choose a job?
It's definitely beneficial to level both of your job's sub-classes as far as their highest cross-class skill. (As already mentioned, that's 34 for Arcanist and 26 for Thaumaturge.)

As to whether it's necessary, in the case of WHM, the combination of THM's Swiftcast with your Raise skill is so incredibly powerful that it's essentially necessary. The others are nice to have.

For when to get them, ideally it'd be nice to get THM up to 26 for the swiftcast skill by the time you get to the level 28 dungeon, or soon thereafter. This is because at level 28 you'll get a Conjurer trait that lets you use Raise while in the middle of combat. The combination of swiftcast (which makes your next spell an instant cast with no casting time delay) followed by an in-combat Raise is incredibly powerful. (In lower level dungeons, where you don't have that trait yet, swiftcast isn't nearly as useful as it is after that point, mainly because your most important use for it —your Raise skill— isn't as useful until then.) Although 28 is ideal, many players do get swiftcast later, while WHM is somewhere in the 30's or 40's, and that's ok too, but you'd generally be expected to already have it by the time you're in your 50's.

Getting ACN up to 34 for Eye for an Eye is something you'll probably want by the time you get to endgame. In fact I'd recommend doing it around the time you get to the game's original endgame at level 50. (Along the way, when you get ACN to 30, you'll already have the secondary classes for unlocking its jobs, so you'll get a chance to try out SCH and perhaps SMN if you're interested.)