Dark Knight: Guide by Raenryong/Support Jobs

Support Jobs
You use a support job mainly for the job abilities/job traits it offers, NOT the stat increases (/mnk is an exception). As such, I will list only the beneficial abilities/traits. "Viable from" means that this subjob is nowhere near the best for this level range but it still adds something. "Good from" means that this subjob is powerful in this level range though perhaps not the best. "Optimal from" means that this subjob is by far the best at this level range. If there is overlap, consider the highest in that hierachy (eg, if it says "Good from: 50-60" and "Optimal from: 50-55", it is "optimal" at 50-55 but only "good" at 56-60).

Warrior
Notes: /war is a very solid sub throughout most of a Dark Knight's levels, although it becomes obsolete after /sam reaches full power at 70+. The Double Attack added is 10%, regardless of whether you have Double Attack merits on Warrior, and this is a very powerful reason to use /war. Provoke is situationally useful, though mainly only in the Valkurm Dunes level range.
 * Viable from: 1-75
 * Good from: 30-69
 * Optimal from: 30-59
 * Provoke at level 10
 * Berserk at level 30
 * Double Attack at level 50

Thief
Notes: /thf puts out large weaponskill spike damage, but in reality its DoT is severely limited compared to the other subjob choices (though it is a very nice farming subjob, where this does not matter so much). On certain high defense enemies it is worth subbing /thf and unleashing a crushingly powerful weaponskill to close a skillchain (often done with a Great Sword). This subjob is NEVER superior in exp, period.
 * Viable from: 30-75
 * Good from: 75 (on certain endgame foes)
 * Optimal from: Never
 * Sneak Attack at level 30
 * Treasure Hunter at level 30 (mainly for farming)
 * Flee at level 50
 * Trick Attack at level 60

Samurai
Notes: /sam is MIGHTY. Gathering TP at a greatly increased rate and putting out super fast weaponskills, speeding up your normal hits and providing you with defenses in the form of Seigan and Third Eye, /sam is the most powerful subjob for a Dark Knight. It is decent at 50 because this is the level when it gets Hasso, and a well-geared Dark Knight can use the 10% haste to outdo /war's Double Attack and Berserk, although /war is debatably still better in that level range. 60-69 it is the most powerful subjob but with little to no defenses (a single Third Eye isn't that much, although best used before a weaponskill!). However, 70+ it suddenly becomes your best subjob in exp and in most endgame events due to its HUGE DoT benefits (both quicker hits, and more weaponskills!). You won't put out the damage numbers you would on /war, but you will produce damage a lot quicker and a lot more accurately due to Zanshin. Just remember that Hasso and Seigan both double cast/recast times of spells, so be prepared to cancel them when casting sometimes.
 * Good from: 50-75
 * Optimal from: 60-75
 * Store TP I at 20
 * Third Eye at 30
 * Zanshin at 40
 * Hasso at 50
 * Meditate at 60
 * Store TP II at 60
 * Seigan at 70

Ninja
Notes: /nin is a compromise: attack for defense. It is NEVER the best damage output, even when Rampage is your best weaponskill due to the reduced DoT. Do not Dual Wield on Dark Knight seriously; it is NEVER your best damage output. Even if you have a Ridill. That said, this subjob is essential in some situations due to the power of Utsusemi; just remember, this is a DEFENSIVE sub. Only sub it when you NEED it.
 * Viable from: 24-75
 * Good from: 56-59, 75 (certain endgame activities)
 * Tonko: Ichi at 18 (stealthing)
 * Dual Wield at 20
 * Utsusemi: Ichi at 24
 * Dual Wield II at 50
 * Monomi: Ichi at 50 (stealthing)
 * Tonko: Ni at 68 (stealthing)
 * Utsusemi: Ni at 74

Dragoon
Notes: /drg is good in the 20-29 range due to the Jump ability, and will also perform well at 30-49 due to the Wyvern Earring, although /war's Berserk will likely still add more. Once /war gets Double Attack too, there is no real comparison between the subs. At 75, /drg makes a huge comeback due to the powerfulness of the Wyvern Earring during zerging, especially with the Kraken Club where you don't want to use a Brutal Earring (more on that later). Jump and High Jump also add a bit of damage to the start of a zerg. At 75, /drg is a powerful sub but with less power than /sam and without the defensive features, so it is not quite as good for general use.
 * Viable from: 50-75
 * Good from: 20-49
 * Optimal from: 75 (zerging with a onehanded weapon)
 * Jump at 20
 * Wyvern Earring at 30 (equipment)
 * Accuracy Bonus at 60
 * High Jump at 70

Monk
Notes: /mnk is viable at low levels if you have nothing else, due to its high HP which is good for survivability early on. It is then a very bad subjob until 75 when the extra max HP is quite good for zerging, although it is outdone by /drg for onehanders and /sam for twohanders. Still, an okay subjob for zerging if you're using a onehanded weapon and don't have /drg ready.
 * Viable from: 1-19
 * Good from: 75
 * Boost at 10
 * Max HP Boost I at 30
 * Focus at 50
 * Max HP Boost II at 70

White Mage
Notes: This is a purely low-level subjob, and is better than /war arguably in the lower levels if your party doesn't need you to Provoke. Also a very powerful solo subjob in those low levels where no other support jobs add anything to the job. I've heard /blu is a powerful subjob at the lower levels but I know practically nothing about BLU. Feel free to post on my discussion pages if you have information about it!
 * Optimal from: 1-19
 * Cure at 1
 * Dia at 6
 * Paralyze at 8
 * Protect at 14
 * Protectra at 14
 * Paralyna at 18