Essentially once you go over level 32 you'll need slightly less than 107% Enhancement values before ED scaling is applied in order to be left with 100% at level 30 (the level you're exemped to in Sirens Call).
For a Mastermind that doesn't care about set bonuses, the idea would be to get at least 107% Acc and 107% Dam in each pet, plus enhancements for whatever other secondary effects that pet might also take/need.
For a Robot MM, Battle Drones and the Assault Bot don't cause mez other than Knockback, so the only thing that's really needed is a SO's worth of endred in Protector Bots. Defense or Healing % are also nice in the Protector Bots if you can fit it in.
The three "Aura" Unique IOs are also well worth getting. Unfortunately since they're not Procs they'll only work at (-3) to the level of the enhancement or above... so you'll need to find level 33 or lower "Defense Aura" or "Resistance Aura" uniques to get the benefit of them in Sirens. The Pet Taunt/Placate Resistance one is of questionable use for Sirens Call zone PvP (or any PvP really).
Personally, I'm aiming for:
Battle Drones: (6-Slotted)
+ 50 Blood Mandate Acc/Dmg/End
+ 50 Blood Mandate Acc/Dmg
+ 50 Nucleolus Acc/Dam HO
+ 50 Nucleolus Acc/Dam HO
+ <33 Edict of the Master (Defense Aura)
+ <33 Sovereign Right (Resistance Aura)
= 114.30% Acc, 114.30% Dam, 21.20 EndRed
Plus 5% Defence (All) and 10% Resistance (All) for all nearby pets
Protector Bots: (6-Slotted)
+ 50 Blood Mandate Acc/Dmg/End
+ 50 Sovereign Right Acc/Dmg/End
+ 50 Nucleolus Acc/Dam HO
+ 50 Nucleolus Acc/Dam HO
+ 50 Defence Common IO
+ 50 Defence Common IO
= 109.00% Acc, 109.00% Dam, 51.00% Def, 42.40 EndRed
Assault Bot: (4-Slotted)
+ 50 Blood Mandate Acc/Dmg/End
+ 50 Blood Mandate Acc/Dmg
+ 50 Nucleolus Acc/Dam HO
+ 50 Nucleolus Acc/Dam HO
= 114.30% Acc, 114.30% Dam, 21.20 EndRed
Note that the HO's aren't needed if you don't want to slot for secondary effects: The cheapest way of slotting over 107% Acc/Dam in a pet is probably 4x level 50 common IOs (Acc/Acc/Dam/Dam) plus 1x level 50 Acc/Dam set IO. This will give you 111.30% Acc and Dam and leave room for an Aura or EndRed IO in the 6th slot.
There's also a particular Purple IO that you'll want to keep an eye out for when issue 11 hits:
+ Soulbound Allegiance: Chance for Build Up
(16.6% chance to get a '+80% Damage buff for 5 seconds' on the pet using this enhancement)
...would fit nicely into the Assault Bot, no? 
excellent response maelwys just what i was after thank you very much
and ill be looking for the new pet proc aswell , i have got both the good pet auras below lvl 30
nice one 
Ps ive posted my build on the pvp section
Hi,
I sort of understand how the ios are affected when a lvl 50 goes to sirens.
What I am after is a suggested ideal slot formation for my mastermind pets to get the best damage I can get in sirens at lvl 50, I am not botherered whether the set boni are active or not.
ie, Would it be better to use my tier 1 pets in a combo of triples below lvl 41, and if yes, what would be the best acc and damage combo be?
From the info I have been able to find this is a very confusing issue for many people.
I akso posted this in the wrong section lol