Let me start off by saying that I agree that ferals are kinda OP atm, and I think that a flat bleed increase is boring.
Blizzard simplified the priorities a lot, and I'd like to see a mastery that makes for a harder playstyle.
Passive for being feral:
Every tick of Rake and Rip gives 1 stack of a buff that stacks up to 20 times, with a 1 sec internal CD(to ensure it doesn't happen too often) and maybe 10-15 sec duration. When it reaches 20 stacks, they are consumed by the next Claw(yes, I did just say Claw) used, and empower it to do 400% weapon damage(arbitrary number, can be changed to whatever to balance it) and makes the enemy bleed for 100% of weapon damage(another arbitrary number, change to something thats balanced) over say, 15-20 seconds.
Cat mastery:
Increases the % of weapon damage done by the Claw bleed by x% per point of mastery.
Yes, this is a flat bleed increase, but the passive makes for a more interesting playstyle, with another attack that goes into the rotation/prio list every 20-25-ish sec.
Does this sound OP? I mostly play PvE, but the long ramp up for this bleed should also make it pretty balanced in PvP, because you deserve to be punished if you let a cat get to you, and let it stay there for long.
Checking back as soon as I've had a few hours sleep.