Just a few random thoughts.
With plant you're going to have SoC at level 8, other than AV fights I wouldn't even waste time using LR because slows are counterproductive to confused mobs killing each other. Again I wouldn't waste time with RI outside of tough AV battles or if you're having difficulties landing your powers. EF will boost the damage on your immobs and Creepers so I would definitely use it often. Mobs that can't be confused could provide reason to use RI and LR but with triple stacked AM I would recommend taking your AoE hold on 1 or two of your trollers for total lockdown.
SoC or creepers are your alpha breakers your pets will pretty much just tag along unless you want to spend the time recalling them into a spawn but why bother?
For radios a solo plant/rad can pretty much run at +0/x8 at lvl 22 without much trouble so no def/res shouldn't be much of a concern. The only problem I could foresee is figuring out a way to make the most of 3 plant/rad trollers at the same time. 
I would not worry specifically about building for Defense or Resistance. However, I would re-consider your RI and EF plan. I think it is best to take both on all 3.
What if one dies? You want all of them to be able to handle all the duties in a pinch. And hey, why resist the DR on foes 3 times instead of once or twice? Why not have that much more -acc vs things that resist it (AVs, etc)? And again, what if you die on one of them but you don't want to lose the fight?
Its something to think about.
Lewis
Random AT Generation!
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Hey All,
Ok, so here is my perma team (I have 3 accounts) so I am rolling with 3 Plant/Rad's.
(which means that as soon as I get Accelerated metabolism, it's perma at 2 min's each and at 22 with SO's and Hasten 3 slotted, I get Perma 3X AM woot).
With all that controlling power do I need to really bother with any Def/Res? yes some sets have it and I have room in my build for both Maneuvers (want that pool anyways for Assault(x2) and Tactics (x1) and Tough/Weave, but with my pets to take the alpha, and the slows/debuffs/holds do I really need it?
Also, I do not plan in taking the 3 debuffs on each toon, so would I be better off with 2 RI and 1 EF or the other way around? I will be taking 3x the LR cause slows are so useful).
Thanks! any adivce would be appricaited.
As for what I want to do with these toons, it's mostly radio mish/AE to FINALLY get some toons to 50.