Yes, the NFL should take a draft pick away from Tomlin and the Steelers, because taking away a draft pick is quite severe punishment. Tomlin interfered with a play on the field. Taking away a draft pick sends a message to him and to others that this type of behavior is unacceptable.
Even if the Steelers have maybe not been on their best behavior this season, that does not warrant the NFL to remove a draft pick from their team. They should be punished in other ways, like sanctions or less home games. There are other, less severe ways of punishing a team.