I wasn't thinking thoroughly during my analysis of my moves. Seeing your post brought up good points.
Frozen Body: I agree on the freeze rate to be decreased to 15% which is similar to ice beam. But you have to remember that most ice-types that would learn this have low defense stats. The only pokemon I could see benefits from this are Mamoswine, Kyurem-B, Walrein, Cloyster, and Glaceon.
As coverage, there is only a few pokemon I can think of: Regirock, Omastar, Golem, Shuckle, Relicanth, and Ryperior.
Mental Flare: While I agree with you on it being powerful, there are some arguments. One is the fact that most pokemon with high special defense stats that could potentially learn this move (common types would fire, psychic, dark, and ghost) usually have unimpressive coverage. Ninetales, and Umbreon are examples. Even in the sun, Fire Blast on Ninetales only does so much compared to Chandelure even without sun support. So having it's Sp. Defense be it's attacking type would benefit it. Me wanting Umbreon with this move only by slight bias. It's more because it truly needs this move to be effective. Steel types shut Umbreon down hard and Foul play or Curse/Payback will only do so much. With Mental Flare, it offers Umbreon a way to bypass bugs and steel, same as other pokemon that get shut down by one or the other like Espeon, Gardevoir, and Bronzong. Two, like Frozen Body, it has only decent power. Ninetales using this in the sun is equivalent to Gengar's STAB shadow ball.
Void Strike: This is all I'm going to say in defense. Besides Dark-Type Judgement, what is the powerful dark type move in the game? Punishment is only good after a +2 stat raise, and by that point, it's going to be KO'd easily because of said stat raise. Foul play is only good on Umbreon and Sableye. Sucker Punch is good only in situations in which the attacker is obviously going to attack, like Gengar's Focus Blast to Absol. That's pretty clear. And either way, most people know that Absol's Sucker Punch is killer, so they would try to switch into a fighting or steel type. Crunch and Night Slash are the only REAL viable options to a physical dark type or as coverage. I fully admit that the dark type priority is unnecessary, and it should at least have recoil, but it is MUCH needed on slower physical sweepers like Absol or Bisharp.
Pulse Beam: Not much is needed to be said. I completely agree with your evaluation.
Spiral Flame: I am VERY surprised you didn't critic this.