It is a Hunter Skill, but it’s not listed on the card. This skill gets great general use in the game, and especially so when bossing with a Bounty Hunter equipped. Maliwan Takedown is one of the places it gets the most use. On the Guardian Takedown you should only spec it if using a Bounty Hunter, or switching to one when fighting the bosses, in which case it will be great.
You can experiment with the points as you wish depending on how much use you will get out of them, just beware that it might make a big difference in the stated scenarios. Two F4ng, Second Intention and Ambush Predator are good alternative choices that you can max depending on what the build you chose already has.