Homebrew: Primal Path of the Slayer

[Kane0]

Okay, the consensus seems to be that Slayer's Quarry is a bad idea, but without it, the Slayer has no utility outside of combat. Maybe he shouldn't be a Ranger wannabe, but I feel like the Slayer should be able to hear rumors of a deadly monster and immediately go after it.

You could just make the creature types flexible, picking a new set at the end of each long rest plus swap one at the end of a short rest, or burning a use of your rage to pick an individual to count as a quarry as a bonus action for 24 hours or something.
Just remove the bonus languages and throw in a tool proficiency or something instead (that doesn't change)

I thought that giving the Slayer a taunt without actually making him tankier might contribute to his role as the guy with a death wish; I hadn't considered how it bit off the Ancestral Guardian.

Grudgelord:
Starting at 10th level, while you're raging, hostile creatures within 30 ft of you have disadvantage on attack rolls against creatures other than you, and any Quarry within this range must make a Wisdom saving throw (DC 8 + Prof + Con) in order to move out of it.

Would doubling Rage Bonus at level 3 be too strong?

Nah, compare with the Zealot.

What about giving access to both Fighting Styles, but adding to them a prohibition of medium armor/shields?

You can't use them both at the same time, but yeah sure. If you couple this with double rage bonus to damage there is now a reason to pick Slayer.
You could change the prohibition to be against metal armor kinda like druids? What is it about medium armor and shields that are so bad you want to avoid?

Which leaves you needing a new ability at 14.