According to Skill Capped definition, Diminishing Returns refers to the game mechanic in which spells become less effective against other player characters if used frequently within a short period of time. Spells that use this mechanic are grouped into categories, effects within the same category share diminishing returns.
Diminishing returns management is important as a rogue since you are CCing a lot during PvP (and even PvE sometimes)

The first time a spell with diminishing returns is used in PVP, it lasts for the full duration (example: blind 10 secs). If a spell from the same category is used within 15-20 seconds of the “end” of the first one, then that spell only lasts for 1/2 of the normal duration (example: cyclone after blind will last 3 secs instead of 6). If you apply a third CC from the same category e.g, another blind or cyclone) then it will last only 25% (1/4) of the normal duration and then the target becomes immune. Below is a Diminishing Returns table to put rogue CCs in perspective with those from other classes.

1) Incapacitates & Disorients Diminishing Returns on TBC

ROGUE ABILITIESShare diminishing returns (DR) withClass
Sap (10s → 5s → 2.5s)Polymorph (10s → 5s → 2.5s)Mage
Sap (10s → 5s → 2.5s)
Gouge (4 → 2 → 1)
Rogue
Freezing Trap (8s → 4s → 2s)
Wyvern sting (10s → 5s → 2.5s)
Hunter
Repentance (6s → 3s → 1.5s)Paladin
Blind (10s → 5s → 2.5s)Blind (10s → 5s → 2.5s)Rogue
Cyclone (6s → 3s → 1.5s)Druid

Sap and Blind are two of the most powerful control abilities of the rogue class because they last 10 secs in PvP.
Any damage breaks the effects of both techniques so you, and your partners, have to be careful in order to benefit from their full duration.

The second thing that you need to care about is diminishing returns.

Tips about the Sap diminishing returns

    • with Gouge : If you plan to open an enemy with Cheapshot-Gouge-Kidney, then you have to make sure that you have not sapped the target before your cheapshot. Otherwise, you will get a half gouge, or worse.
    • with Polymorph : If you play arenas with a mage, it is essential to synergize your controls so you do not mess up your CC rotation… It is one of the most important rules as RM. In lower rates, you often meet rogues doing bad gouges on enemies which makes the following sheep a lot less efficient. But even 1/2 DR sheep remains as one of the Best CC.

Tips about the Blind diminishing returns

Blind / Cyclone DR is one of the most important rules of RD. Do not waste a blind because you did not pay attention to your mate’s cyclones! This can be a game-changer and result in a complete victory for your opponent!

2) Stuns Diminishing Return on TBC

ROGUE ABILITIES Share diminishing returns (DR) with Class
Cheap Shot (4 → 2 → 1) Bash (5s → 2.5s → 1.2s) Druid
Pounce (4s → 2s → 1s) Druid
Hammer Of Justice (6s → 3s → 1.5s) Paladin
Cheap Shot (4s → 2s → 1s) Rogue
Shadow Fury (2s → 1s → 0.5s) Lock
Intimidation (2s → 1s → 0.5s) Hunter
Charge (1s → 0.5s → 0.2s) Warrior
Intercept (2s → 1s → 0.5s) Warrior
War stomp (2s → 1s → 0.5s) Race
Kidney Shot (6s → 3s → 1.5s) Kidney Shot (6s → 3s → 1.5s) Rogue

Rogue Stuns specifications

Cheapshot (CS) and Kidney Shot (KS) are the stun abilities of the rogue. They are extremely useful to lock down a target while damaging it.

Kidney shot: KS only shares DRs with itself, but it does not mean that you are safe from DR.
The DR is set on dynamic timers, and not on a unique duration. Sometimes, a DR will last 15sec, and sometimes 20sec.
Truth is you are most likely to get outplayed by a DR if you do a 5 combo KS (6-sec duration) and then spam it when your cooldown is back.

Quick explanation:

            • Kidney Shot Cooldown: 20 sec
            • Kidney Shot Duration (5cp): 6 sec
            • The minimum time span between 2 (5cp) Full KS: 14 sec = DR

NB: DR starts when a control ends up naturally or breaks. So if your Kidney is trinketed, your next KS (right after your cooldown reset) won’t be degressive.

Cheapshot: This ability shares DRs with a lot of techniques. If you are playing with another melee DPS, there will be some shared DR between your CC techniques. You need to be careful with that. In this case, you may prefer to open with Garrote or Ambush.

NB: Contrary to WotLK, DR’ed CS is not very worth using in terms of efficiency.

3) Silences Diminishing Returns on TBC

Garrote (2s)No DR on silence effects on TBC!
Imp Kick (2s)
Arcane Torrent (2s)

In TBC, there are no DRs on silence effects. This means that you can chain two garrotes or combine silence, garrote, garrote with your partner to lock down an enemy during 8 seconds or more.
This is one of the main strengths of TBC rogue/caster gameplay in arenas.

Now you know everything about the diminishing returns of The Burning Crusade, so it’s time to manage them all so you can build the perfect synergy with your arena partners !