-The only spec that uses poisons.
-Poisons are no longer a long term "buff"
-combo point builders apply short term poison buffs (Due to this combo points stack on the rogue rather than the target) and pseduo alchemy style potions.
-Poisons have different effects such as damage/DoT snare/stun, debuffs on the target, potentially self healing with it.
-Finishers change based on the poisons applied (things such as applying a concentrated version of said poisons to one target or a longer lasting version of the same poison (this would be the difference between a direct damage to the target, or causing each of your hits to apply a weaker poison damage. or between a stun to the target, or a longer duration snare) , a weaker version to multiple targets through a poison gas.
-high DPS, decent "on call" burst, but you have to work up to it
-can have up to 10 poisons applied, although only 5 can be used per finisher
-I'd like to see mutilate have various potions/poisons that provide utility. Drink a poison to build resistance to nature damage (takes 10% of my HP and gives me x% resistance to nature/magic damage for x seconds). Drink a poison that makes your body work harder, gaining more run speed at the cost of x health or y health per second.
-Only spec that uses slice and dice
-Main focus revolves around energy regeneration.
-Each auto attack that lands regenerates energy, although base energy regeneration is lowered dramatically. potentially gain energy based on dodges/parries.
-All finishers consume all energy, but increase in effectiveness based on the energy consumed. Due to this as the fight goes on your DPS will increase (as combat is a spec based on actual out of stealth fighting) while capping off at a point when you can afford to do 100 energy slice and dices (at which point you would have the maximum energy regeneration)
-CP builders as well as finishers that focus around survivability (kinda like combat readiness) as well as the return of repost (or a similar strike to be used after you are parried/dodged, or after you have been parried/dodged)
-less around keeping things up such as rupture/revealing strike, more about -now- damage.
-Drop blade flurry, I love its existence but it’s a rather boring mechanic (second target near you? press this one button and forget about it). Gain 2-3 target combo point builders (probably the type that does, say, 80% damage each, with 3 targets it does 70%)
-Since we are talking "combos", and some of the best involve multiple people, I’d love to see a way to allow you to do single target attacks on multiple people are part of the same combo. I'd like it to be more interesting, but this could be as simple as having redirect have no CD for combat
-Combat steals a mastery similar to sub's, it’s what allows their finishers to be more effective per energy used.
-4th bar! mechanic similar to demonology warlocks. As you perform finishers, you build up a "shadows" meter. Whenever you so decide you can "slip into the shadows" gaining resistance to AoEs, potentially increased evasion, armor penetration (replacement for "find weakness") and most importantly, allows stealthed abilities to be used out.
-Mastery increases the effectiveness of the AoE resistance, armor pen, and potential evasion increase. maybe increases the duration per point (harder to balance, not likely)
-I'd like to see a finisher that puts you into actual stealth for x seconds. could be too OP in pvp
-I'd like to see sub have more situational "toys" like smoke bomb.
-Sub would have the best burst, but likely lowest actual DPS.
all 3 specs would have their best situations, and would play very differently.
Assassination would be about managing your poisons, using the right poisons for the right situation. It should keep a similar feel to managing your combo points. While a high DPS spec, due to combo points stacking on you as opposed to your targets it’s a great candidate for fights where you stay on the boss the entire time, but still good at switching between targets. very likely the best when you have times where you aren’t within melee range of your targets (applying poisons to your daggers as you run between targets or when you have to move away from melee range). Likely the best AoE dps rogues have to offer.
Combat is all about staying active. While you still worry about managing your combo points, your energy is key. Combat's DPS would be good, but you take a substantial hit when you have to be away from the boss for too long. Combat would be the best at fighting a moderate number of targets relatively close together. Switching targets would cost little/no dps as combat is using "now" damage (as opposed to DoTs like deadly poison that build up) while running between targets would cost a decent bit. Best cleave damage while only decent AoE damage and good single target damage. Combat is a great candidate for a time when the raid needs a "weak tank", example in current content would be strengths on will of the emperor.
Sub is about managing your shadow meter, as well as combo points. Sub would be the worst candidate for a fight where you have to switch targets often, but great against highly armored targets or fights where you need controlled burst. The single target dps would likely be the lowest (while still viable) as well as likely the lowest AoE dps, while the higher amount of survivability would allow sub rogues to stay in longer through tougher situations than the other specs, making them equal to or more viable single target DPS in many situations.
sorry for any spelling/grammar issues or redundancies, this was written off the top of my head between customers at work :P (and my spelling kinda sucks anyways)