Plant/kin + Plant/Cold would be interesting
Fire/Kin + Fire/Rad get's my vote.
Consciousness: that annoying time between naps.
I guess I don't know for sure what's best for dual boxing, not having done it, but I would think you'd want to minimize how much detailey power application you're doing. IOW, I'm not sure Kin and Storm would be great for that purpose, unless the way I imagine you doing it is all wrong.
Multiple Fire/Rads is great because it's just, you know run in and let things die around you, practically.
Choosing a Controller V2 | Splattrollers | Plant/Rad | Fire/Storm | Mind/Emp & Mind/Rad
Weird Controller Powers | Conf & XP/Time | Controller Damage
Being a Healer | The word Necessary | Natural Concept Characters
Speaking as a long time dual-boxer and more recent triple boxer. Any time you split what sets you take you set yourself up to have one character being much weaker than the other.
While a rad/kin duo might be fun when each is played by a separate person when played together unless you really can split your mind in half you end up with one character that does most of the work and a follower. And if you are using the alt+tab method that will be even more the case.
For example a Fire/Kin and a Fire/Cold. The fire Cold doesn't get any shields so will be quite a bit less resilient and while the kin will have sufficient heals for the kin what if the cold is too far off from the kin to get the heal? And even with countless hours practice on my fire/kin team one of the followers fairly often is slightly too far off to get the heal.
If that's the deal you want I'd suggest going with an all out damage dealer and a buff follower.
If you like me are going to software box I'd suggest picking two characters that synergize especially well and go with two identical (or as near as damn it) builds.
As for what to try... that would depend on your play style and what you enjoy. I personally love my fire/kin trio (started as a duo), Mind/Rad duo is fun as is my Grav/Rad trio. I have also played around with Emp & Kin defender duos/trios and fire/nrg blasters.
I've run Dual Box a few times prior to level pact. I would run with fire / kin and use my wife's grav / rad and just leave her on auto heal running behind me. My fire / kin would do all the work and add extra heals when needed. I'd use her account more for buff/debuff and auto heal. We have two computers to do this with (desktop & laptop) which made it easy to leave her targeted on me and just use a keystroke here or there for extra holds or set debuff. Since level pact, I just get to play twice as hard for half the exp.
Some controller builds that we've used were (Fire / Kin attack with Grav / Rad support(from above)),(Earth / Sonic attack with Ice / Storm support), (Illusion / Trick Arrow attack with Mind / Emp support)
(I've also found that tank / defender, scrapper / controller, master mind / corruptor all work well too. )
Demonfest - 50 - Demon / Thermal Mastermind
Covered Shadow - 50 - Dark Melee / Shield Scrapper
Thanks for the replies all. I'm also using a two computer (well pc and laptop) set-up which makes it a little easier to at least try to play both at the same time (keymaps for powers really helps too). In the past I've tried a couple of damage dealer/buffer combinations which only require the second character to fire the occasional power (all out fire blaster with permanent emp support is a joy 
) but this time wanted to try something a bit more involved.
I've given my original thought of a plant/storm with plant/kin support a go and have got them to lv19 in a couple of days. My initial impressions are that it's pretty binary - I either lay waste to all around me or eat floor in 5 seconds flat. I run in, fire off one or two seeds of confusion depending how brave i'm feeling, lay freezing rain down, and spam roots and the odd kin power (if I remember) until everything is 'arrested' into next week.
Or I run in, seeds doesn't hit enough people and both characters get a fun trip to the hospital ... Having said which I'm finding it hard to not run missions set to 6 people so might have only myself to blame
Twin /colds could be interesting and would definately be safer but I'm not sure about the damage. I'd do fire/rads (or plant/rads) but I've done rad to death over the years.
My best dual-boxing setup is a fire/kin +fire/sonic. Fire/cold does make an attractive alternative, but I still am leaning to the Sonic because 2 powers are toggles (dispersion and disruption) and the 2 ally shields just need to be applied every 4 minutes. Cold's toggle gives stealth, which is very very nice.
Anyway, it's moot since it looks like you've already made your choice, which sounds like it should be a fine one.
Global = Hedgefund (or some derivation thereof)
Grab the Synergy programme off my website (its free, and in my sig) and you can play two active characters at once who coordinate their attacks.
Ive got a Fire/Rad pair, and they do very well as you might expect.
On Defenders, I found Kinetics and Force Field really shored up each others weaknesses - it may be worth trying this on Controllers. A (mostly) un-mezzable Kin is great to play.
I currently often pair up my Earth/Kin with a Sonic?energy defender for great results in a similar vein.
Ive generally found /Sonic to be an excellent second-box set since it has no awkward location powers (except Liquefy) and no real need to look at the secondary screen ever.
For primaries - Illusion would make a bad second box set due to the constant need to resummon using location based powers. Gravity would be good except for Wormhole, one of its key powers, needing screen attention to use.
Plant works quite well (from practice) but requires re-summoning Carrion Creepers and lining up the cone fro Seeds of Confusion.
Mind is probably one of the best sets for a second box character.
Still going reasonably well with the plant/storm & plant/kin. Looking at the various combinations that everyone has suggested I can see merit in them all. I'm almost completely reliant on seeds of confusion and often wish I had some shields of some kind to apply to the main (who is invariably in the thick of it). Having said which I'm addicted to the permanent speed boost and so would be loth to give up the kin support.
I'm wondering if /cold would have been a better choice than /storm though. I was thinking that I'd get some use out of tornado and lightning storm as extra damage but in all honesty since getting carrion creepers on them both things are dying so quickly I'm not sure I'll have the time or the need to use them. Storm also comes with powers that I'm unable to use effectively as they rely on position (gale and hurricane) and the extra debuff potential in cold looks very good. 35 is a long time to wait for sleet when storm gets freezing rain at 16 though.
Hi All,
Long time forum lurker, first time poster. I've been tempted back after a few months away from the game mainly by the new difficulty options available in I16. I'm thinking that this should make dual boxing more of a challenge - more mobs, more carnage, more
So I'm trying to work out what my new duo should be (more or less sure I want them both to be trollers). I'm pretty comfortable with at least 60/40 dual boxing so don't need the second toon to be completely passive. I've payed in a Fire/Rad superteam before so am leaning away from that (particularly the Rad part which I've played on lots of toons).
Plant/Storm backed up by a Plant/Kin? I've been playing a while but am no market pvp'er so I'm not looking for anything that requires billion inf builds. Having said which I can mow through posi's for the qol uniques where necessary.
Any thoughts?