I'm used to scoreboard features and have been doing this for a long time.
However in 1.8 (all builds until now) I cannot disable friendly fire in a team. That is to say I cannot prevent players from the same team to hurt each other.

Here is the test scenario.

• Build spigot-1.8-R0.1-SNAPSHOT.jar (any version, I've tested it with the last one git-Spigot-47b1dff-f233e7d)
• Create launch.bat with :
  java -Xmx2024M -Xms256M -jar spigot-1.8-R0.1-SNAPSHOT.jar nogui
  pause

• Accept eula.txt and restart
• Activate command blocks and restart
• Connect with two differents accounts
• Run these commands in commands blocks :
  /scoreboard teams add test
  /scoreboard teams option test friendlyfire false
  /scoreboard teams join test @a

• You can check with /scoreboard teams list test that the two players are in the same team
• You can then check the bug : the two players in the same team with friendlyfire set to false can still hurt each other.

I have also made a video with this exact same scenario.
https://www.youtube.com/watch?v=Y7rvJ8byAi4