I have to disagree with a lot of your choices. I have experience with almost all the powers you listed and have found great value in all of them at some time or another. Let me highlight some:
Rain of Fire - A smart Blaster (or Corrupter) knows when to use this power to get the maxium benefit. Rain of Fire + Tar Patch, Ice Storm, Lingering Radiation, Sleet, Quicksand, or Freezing Rain? Wow.
Lightning Clap - "Oh crap, I'm surrounded and they're all pummeling me!" *POW* Most of your enemies are now rolling around on the ground and/or disoriented. This gives you breathing room to get away or pick your targets to finish off before the disorient wears off.
Stun - A very useful power for disabling an annoying enemy long enough for you to either dispatch them or their pals without worry. You need not worry so much about mez effects on your blaster if you have this power handy. Sonic's Screech is the same way.
Salt Crystals, Flash Freeze, Mass Hypnosis - any AoE sleep is a great power to have handy, especially if you solo any. Suddenly giant mobs of enemies are not as much of a threat if you sleep most of them and pick them off at your leisure. "Oh no, we've aggrod that other giant mob of foes and we're not finished with this mob set yet!" Time for an AoE sleep on spawn #2!
Black Hole - Same idea as with the AoE sleep powers. BH has been invaluable the few times I've had to use it. The best thing you can do is have a Macro or Bind ready to go when you use this power, so your team knows what's going on and hopefully doesn't expend too much power on unaffectable mobs.
Inertial Reduction - one of the things I love about Kinetics is the inclusion of travel powers within the set. Why bother taking pool powers when you have an unsuppressable one at your command? Unless you're going for the benefits of Combat Jumping and Acrobatics, Inertial Redux is Super Jump without a prerequiste.
Thunder Clap - Disoriented Enemies don't fight back.
Confront (Scrapper Taunt) - No Srappers are not Tanks, but I can't count the number of times I have saved a teammate some debt by having my scrapper taunt on hand. It's also nice to catch runners without having to chase them down.
Fire Breath - it may be only moderate damage, but if you know how to line up your cone well, being able to hit multiple enemies in one shot with a lesser-resisted damage type can really mow down a spawn.
As for Hurl - well it's certainly nice for a melee toon to have some kind of attack to keep a fleeing enemy from fleeing.
A lot of these powers are situational. They're not used in regular battles as part of a normal attack chain. It's why they are often passed by or scoffed at. If you plan on being able to use these abilites all the time you have the wrong mindset for their purpose. I bet most people would think that Detention Field was worthless, until you face an Ascendant Boss who puts YOU into a DF and takes you out of the action.
