If you have a character that is on the following quest:
A Test of Valor - Quest - World of Warcraft
And you would like to also complete the same quest on another character. You simply need to have the other character logged in on another wow account under the same battle.net when you reach the 3000 requirement on the main character. My rogue was behind my hunter in getting the required sigils which meant I started this quest at like 400/1000 valor for the week where as my hunter started at 0/1000 valor for the week. When my hunter finished the 3000, the rogue also got it for being on the same battle.net at the same time.
TLDR:
Be On Test of Valor on two chars.
Have Both Chars online at same time
Complete 3000 Valor on the main character
Even if your alt is at 0/3000, It should get the credit and complete the quest.
Notes:
My characters were same faction on same server and in a group when my hunter completed the 3000 valor points.