As suggested by MartilloNegro Follower support is now in Tarzan Yell
How it works:
Works with Follower overhauls as well
Right now follower support only works for up to 4 followers, and there are some slight, and non-essential bugs. This will be drastically improved in 4.0
When you yell, each follower will wait a little while, and then follow your example. This interval is randomized, so it doesn't feel so mechanical.
Your follower's screams will also have a randomized pitch variance, again to make it feel a bit more organic. Right now followers will simply use your selected scream, but expect the option to select a different option for your followers in the future.