Shadow Warrior

You can pre-buff Shadow Warrior. Shadow Warrior will keep the bonuses at the time of the cast, even if you change equipment.

Patch 2.4

Blizzard wrote:

Shadow Warrior

• Casting Delay reduced from 6 seconds to 0.6 seconds

• Casting Delay will no longer share its cooldown with other skills that have Casting Delays

• Tooltip updated to now display Casting Delay

Like the Shadow Master, when a Shadow Warrior uses a skill for the first time, it "learns" the skill at a slvl of 1/3 the slvl of Shadow Warrior, plus 1/2 of the player's slvl in skill being "learned", rounded down with a minimum of 1. This calculation includes "soft points" (from equipment, et cetera) to the player's level in both Shadow Warrior and the learned skill.

Once learned, the Shadow Warrior "stores" this slvl value. Shadow Warrior benefits from synergy bonuses, with the "stored" slvls being used for synergy calculations. Unlike the player, a Shadow Warrior is not limited to 20 ranks in any given skill for purposes of synergy calculations.

For example:
suppose a Shadow Warrior is summoned by an Assassin with 14 ranks in Shadow Warrior, 20 ranks in Fire Blast, and 20 ranks in Wake of Fire as well as +10 to all skills. Initially, the Warrior will have no ranks in Fire Blast or Wake of Fire.

Upon first using Fire Blast, the slvl will be set at [(14 + 10) / 3] + [(20 + 10) / 2] = 23. This will result in the skill dealing 124 - 159 fire damage.

If the Warrior later uses Wake of Fire, then uses Fire Blast again, Fire Blast will have an 11%-per-rank synergy bonus that will refer back to the slvl 23 Wake of Fire. Thus, the later Fire Blast would deal [124 (1 + .11 * 23)] - [159 (1 + .11 * 23)] = 437 - 561 fire damage.