What is your secondary?
Also, PB/PBU do very little in regards to Storm Summoning.
World of Confusion tends to be a very sucky power, though I've found a use for it on my paper version of my Elec/Earth/Psi Dom. Just need to hit level 44ish to be able to try it out.
Soul Drain from Dark/Soul is more productive if you're wanting a damage aspect.
Electric is a very popular one because of the immobilize ST power. It does -kb which is very helpful for starting up everyday use of Tornado instead of just on EB/AVs or storm tanking. It also has a hold.
Mu Mastery also has a hold and conserve power, you just have to take the resist or power sink to do it. Not to mention that it has a pet.
Leviathan tends to be the weakest set imo for Defenders. It does have a hold, an oh crap button, and a pet. Though, all of those are the top 3 powers from the pool.
Mace has a crazy defense power for Smash/Lethal/Energy on a Defender, it has a hold, and a pet.
50s: Bla- Arch/Mental Cont- Mind/FF, Earth/Cold, Ill/Therm, Earth/Rad Dominator- Plant/Psi, Elec/Earth Corr- Fire/Storm, Arch/Sonic, Rad/Kin, Beam/Sonic, Psi/Time Stalker- Elec/SR Def- Storm/Dark, Emp/Psi, Dark/Elec, FF/Arch, TA/Ice, TA/Elec, Kin/AR, Cold/DP, Traps/Psi Scrap- Fire/Shield Tanker- Dark/Mace, Ice/Kin Brute- Claws/WP, SS/Energy, BS/Elec
I'm a fan of Power Mastery mostly for conserve power which is the best endurance recovery power for a Storm Defender in my experience (because we go through endurance so quickly). Power Build up, although not as useful on Storm as some sets does make for a very nice series of supercharged heals when you need them, and the damage boost on enemies already debuffed by freezing rain isn't exactly something to scoff at. Since power boost doesn't have the +damage component, it is much less useful.
Your secondary would definitely have a big impact on whether any of the holds are useful. If you don't have anything to stack it with, I'm not sure that I would bother (although having some sort of mez to take troublesome Lts. out of the action is useful, although many secondaries already have something to fit that bill).
As Stormy Darkness said, world of confusion is not particularly useful. It's radius is fairly small, and you have hurricane to keep you out of melee. If you are often in a range where WoC would be useful, I would suggest there might be better ways to play your Stormie.
I'm currently using Mu Mastery because it gives me conserve power, as well as allowing me to reach the defender resistance cap for smash/lethal/energy with the help of the cardiac alpha slot. A very nice trick in my opinion.
Of course, one of the most popular choices which is not on your list is Dark Mastery to stack oppressive gloom with thunder clap. (As my earlier melee comment may suggest, this is not a strategy I am particularly fond of, but it is popular). And as Stormy Darkness said, Soul Drain is an awfully nice buff.
The other popular option which Stormy Darkness mentioned and is not on your list is Mace Mastery for Scorpion Shield to soft cap smash/lethal/energy. Personally, I prefer leveraging hurricane to protect against melee and soft capping range, and taking a set with resistance for greater survivability, but if you want a cheap soft cap (Storm can do it with little IO help if you're willing to take a slew of defense powers (weave, maneuvers, hover, combat jumping) that's the way to go.
Draggynn on Virtue: lvl 50 Storm/Psi, 1389 badges
Draggynn's Guide to Storm Summoning(Gale-Tornado, updated 6/25/2011)
Avatar by Wassy full reference here
I should have mentioned that my Stormie is /Dark, if that makes a huge difference. I realize this gives me the option of Thunderclap -> Dark Pit -> Oppressive Gloom, for mez stacking, but I prefer to just use Hurricane if I'm planning to get into melee range to do mitigation. I still have problems with LTs that like to mez (Carnies and the like), as my only solution to those (at least solo) is currently to open with Tornado - hence why I like the idea of getting a Hold.
I should have clarified with regard to World of Confusion that it's not something I feel I remotely need for mitigation. I just like the idea of having a Confuse.
I'll look over Soul and Mu.
Well, I have a Storm/Dark as my "main", but there was/were a few things that I wasn't completely understanding when I chose my build, and since the addition of incarnate powers some of the reasons I did what I did have become somewhat of a legacy build yet to RP standards now fitting (because I fit it in).
My Storm/Dark has Power Mastery. I took PBU, thinking that LS and/or Tornado would get the extra debuff/damage for the entire duration, but I believe that's untrue. Then again, I've only really noticed the damage difference with PBU on my TA/Ice when using Ice Storm/Blizzard. The damage increases goes for a bit, but then goes away after the duration is up. So my initial believe of a big buff to Tornado has been somewhat squashed, though untested formally by myself.
I also took the resist shield to help plug holes that Steamy Mist didn't cover (Smash/Lethal is a big hole if you don't have tough).
I also took Force of Nature for two fold. One, as a "oh crap" button that doesn't make me stop throwing tornadoes, LS, and FR along with Dark Pits and cones. Eye of the Magus only works for so long... The second reason being the +endurance aspect. If my endurance is starting to suffer in a long battle or I'm just not paying attention to my endurance for a while, I pop FoN and it'll stay even instantly and work back slowly if I'm still slinging stuff.
Since I realized PBU's less usefulness (though still helpful for +dmg on cones, longer stun on Dark Pit, and bigger -to-hit debuffs from my cones) in reference to Tornado and FoN being covered by Ageless and smarter tactics/use of Eye of Magus and whatnot, it's become a "if everything else fails" power that never really gets used. That is with the exception that I've not done many speed runs with him any more, I have a few that are much better designed fro speed runs and use those characters in place of him. Speed runs having several minutes of capped resistances is nice, even with the endurance crash.
I may have to actually look at his build (again) and see if I want to actually alter his build to maybe get more productivity out of it. It's been a while since I've attempted to make a new build for him.
50s: Bla- Arch/Mental Cont- Mind/FF, Earth/Cold, Ill/Therm, Earth/Rad Dominator- Plant/Psi, Elec/Earth Corr- Fire/Storm, Arch/Sonic, Rad/Kin, Beam/Sonic, Psi/Time Stalker- Elec/SR Def- Storm/Dark, Emp/Psi, Dark/Elec, FF/Arch, TA/Ice, TA/Elec, Kin/AR, Cold/DP, Traps/Psi Scrap- Fire/Shield Tanker- Dark/Mace, Ice/Kin Brute- Claws/WP, SS/Energy, BS/Elec
I went for Dark Mastery on my DP/Storm Corruptor because the synergy seemed nice.
Steamy Mist have Fire/Cold/Energy Resistance so adding Dark Embrace gives you resistance to everything except Psionic.
Dark Consumption helps a bit with Storms heavy endurance usage (although not as much as Conserve Power)
Finally Soul Drain works well when combined with Hail of Bullets (and the Dark Mastery version if Soul Drain is much, much better than the Soul Mastery version).
That is very true, regardless of what power sets you are playing, if Soul Drain is a heavy weighed power on what APP you pick. Dark wins over Soul. It's still nice if you want SD and PB.
50s: Bla- Arch/Mental Cont- Mind/FF, Earth/Cold, Ill/Therm, Earth/Rad Dominator- Plant/Psi, Elec/Earth Corr- Fire/Storm, Arch/Sonic, Rad/Kin, Beam/Sonic, Psi/Time Stalker- Elec/SR Def- Storm/Dark, Emp/Psi, Dark/Elec, FF/Arch, TA/Ice, TA/Elec, Kin/AR, Cold/DP, Traps/Psi Scrap- Fire/Shield Tanker- Dark/Mace, Ice/Kin Brute- Claws/WP, SS/Energy, BS/Elec
After taking a few years away, I'm back and currently working on my old Stormie. He's currently closing in on 41, and I'm having trouble deciding on an APP (or Patron Power).
I've narrowed down my choices to Soul Mastery (for Power Boost and a Hold), Power Mastery (for Conserve Power and PBU), and Psychic Mastery (mostly for Dominate, but World of Confusion looks interesting).
If anyone has experience with some of these combinations, I would love some input.