First of all, you should note that HARP is semi-viable in S4 (It was the rogue ace spec during S2). By that I mean that the standard Hemo spec will always be ahead of it, and HARP falls somewhere between that and Mutilate (depending on the comp you're running).
The main difference between S2 and S4 HARP is that in S2 Prep reset the cd on your AR, whereas in S4 it doesn't.
Secondly, if you're gonna run HARP, you should know it's useless unless you spec into maces, as the rng macestun made it viable. So, as far as weapons go: Main-Hand > Slow Mace // Off-Hand > Fast Mace (1.5 speed).
Gems: The standard gems you'd use in any other Rogue spec.
Gear: The standard gear you'd use in any other Subtlety spec.
TALENTS --> *NOTE: This website is known to have some tooltip errors, but it is the best I could find. SOME OF THESE TALENTS ARE NOT AS THE SITE DESCRIBES*
http://wow243.gamestool.net/roguet.php? ... 1210400000
Explanation -->
---SUBTLETY TREE---
Master of Deception: No Comment. Must have.
Dirty Tricks: Must have.
Camouflage: I personally like to have it maxed. Can be used to just dump points in, but imo it is useful.
Ghostly Strike: Useful. Not a must, but useful.
Initiative: ^ (You can swap points in Camouflage or run without Ghostly Strike to have 3/3 Initiative, up to you).
Elussiveness: Must have.
Serrated Blades: Must Have.
Preparation: Must have.
Hemorrhage: Must have.
Dirty Deeds: Must have.
Heightened Senses: Very useful. Not 100% must, but at least 1/2 is strongly advised.
Deadliness: Very useful. (Yes, it is better than Master of Subtlety.)
For fairly obvious reasons Improved Ambush is useless. Setup, Opportunity and Sleight of Hand aren't all that bad, it's just the other talents outshine them.
---COMBAT TREE---
Improved Gouge: Must have.
Lightning Reflexes: Since Sinister Strike is useless, it serves as a filler.
Precision: Useful. I'd mainly pick it just to get the Dual Wield spec tho.
Improved Slice and Dice: Must have.
Endurance / Improved Sprint: Must have.
Improved Kick: Must have.
Dual-Wield Spec: Pretty good. You can go HARp with 0/5 in this talent and dump those points to Imp Evisc or Malice from Assassination, but arguably DW-Spec is better. (especially if you use SnD a lot).
Mace Spec: Must have.
Blade Flurry: Depends on personal taste.
(There is no reason to get 3/3 Aggression, as you could spend those 3 points elsewhere (e.g. on Improved Evisc so you gain 9% evisc damage in supplement)).
Adrenaline Rush: Must Have.
Notes:
1. You can experiment with your points spent on Deadliness/Dual-Wield-Spec/Malice/Improved Evisc and find a personal favorite variable of the spec I linked.
2. HARP is what Rogues call a "Rushdown" spec, which means you're pretty much playing like a mentally hindered Warrior on steroids. Great for getting quick pressure up on a single target. You just have to kill things. Fast.
I don't play TBC / on SF anymore due to PC tech problems, but I sometimes check the forums. If you need anything else, reply here and I'll respond as soon as I check back.