I have experience Bots/storm to level 50 success. My most dedicated teammate during this period was a Necro/storm. I highly recommend either, and I sure there are others just as lethal.
Triumphant Defenders Forever
Psylenz FF/Psi, ArticQuark Storm/Rad, Symon BarSisyphus Bots/psn, Max VanSydow Thugs/Dk, Cyclone Symon Bots/stm, Blue Loki Ice/Cd, Widow 46526
HelinCarnate:OMG it is so terrible. I have the option to take 3 more powers but no additional slots. Boo F'ing hoo.
robots/storm!
- all ranged - don't care about KB
- very durable - O2 boost is enough for spot healing
- def based - use call to arms & edict to boost the pro-bots bubbles by 10%
- good money makers too - look for AE missions with banished pantheon (they love energy & fire attacks)
you'll want -kb electric fences to help keep stuff in burn patches and tornado, but you won't be waiting for it to be effective - r/s is a strong run 01-50
if you have the scratch, drop an achilles -res in frz rain and a second one in tornado
also, force feedback in LS and hurricane will serve you well
storm's full of proc-y goodness: you can have chances for -res, smashing, lethal, energy, & negative energy all in frz rain; damage proc, speed proc, and hold proc in LS; damage and -recharge in snow storm; etc.
Thugs, Mercs, or Bots. You'll want a ranged set as there's lots of aoe moves to hold foes in, so then it's like ducks in a barrel.
thugs will add aoe fire to it and have stacking defense
Bots are resistant to lots of stuff including psionic and also pump out fire aoe as well as brutal energy moves and flying stun grenades
Mercs have mad firepower, stun grenades, tear gas, lrm missles, and other crazy tricks
All 3 are great, but Bots is the only one I've gotten to 50.
For a character with a grim, arcane, evil aura, it would be difficult to top necro / storm. Its a combo that offers loads of "atmosphere" 
Also, the -to hit from necro minions stacks very nicely with the -to hit from hurricane, potentially putting mobs at the "to hit" floor. Plus, the controls offered by the lich neatly complement the softer damage mitigation tools in storm. Finally, steamy mist protects melee minions from fire, cold, and energy damage, which happen to be three particularly common sources of AOE damage.
A vote for Necro/Storm here, was insanely fun for me. Herding things into a corner and letting my pets just tear them apart.
Anything/Storm is gonna tear pretty much anything up.
I personally like Thugs/Storm, them being mostly ranged is a great help, while you also have a nice punching bag to soak up aggro.
I have also heard good things about Necro and Ninja, and Bots is always a crowd favorite. Mercs is alright, but they don't have anything that really stands them out. I have yet to try them with storm, so don't take my word on it.
Mngwa I think your Avatar's having having a seizure!
Mngwa I think your Avatar's having a seizure!
Thugs/Storm is simply too much fun. That's personal experience; I'd also consider Bots or Mercs.
Ninja/Storm with group teleport. Absolutely one of the funnest MMs I have ever played.
Let me explain... One of the biggest issues with ninjas is getting them into melee so they can do the most damage. group TP fixes this issue, as well as keeping minions within steamy mist and auras.
My usual lead off is hit group TP and Q freezing rain. Hurricane is also very useful in doing this for the -acc debuff that all the mobs will get nailed with.
It's absolutely the wildest ride of a MM I have ever played and loved it!
Wassabi Grav/Kin 50 (before badges/accolades were in game) Pinnacle
Miss Command Bots/Traps 50 Justice
*others left off due to space issues
I really enjoy storm and want to play a stormymind but dont know which minions I should shackle to my control. Opinions?