Mobile and at work but as I sit here on my break I will do my best to explain quickly why it's so bad (old arguments from a million years ago still apply).
Body Armor: this is an inoffensive free resist buff and IO mule, but IMO the free nature of it does not justify its lower resist values compared to something like Temp Invul or Fire Shield. It's especially worse than the defense buffs from something like Frozen Armor because defense is so much easier to stack. It'd be a worthwhile sacrifice if the set had other powers worth taking, alas...
Cry Freeze Ray: This is the only standard power in the set that's comparable to the other APP holds. You could argue it's worse due to redraw (it does draw a gun IIRC) , but overall it's simply passable.
Sleep Grenade: In my opinion this is the first truly awful power in Munitions Mastery. First, there's a weapon redraw. Secondly, I always felt the value of sleeps was dubious at best. 99% of the time your first action against a group of enemies is to open up with a huge AOE based alpha strike or a melee guy is gonna run in and grab aggro. What does a sleep afford you at this point? The enemies were already blissfully unaware of your presence. This power adds nothing for the player. Compare it to Bonfire or repulsion bomb slotted for - KB. It's vastly worse. Bonfire provides massive AOE control and good damage. Repulsion bomb gets you good KB/KD and a disorient. Force and Electrical get you God-mode powers. As far as the "utility" power in the set, it's garbage.
Surveillance: Finally, a decent power. Oh wait, Flame Mastery gets an AOE version of this power, and the whole rest of the powerset is better than anything else in Munitions? Damn!
LRM: Okay, I suffered through MM and finally got to the good power. BIG ASS AOE. Sounds great. Except let's see... Awful recharge time (4 bloody minutes), mediocre damage (and it just so happens that it's purely s/l damage as an end-game power that the majority of enemies are highly resistant to) high endurance cost, especially if you clicked too soon after moving and and accidently triggered its ridiculous interrupt penalty. In my testing on Justin there is absolutely no situation where I would use LRM over literally any other AOE. It's impossible to use in combat and I would take a KD slotted Bonfire over LRM any time, period.
I don't have a lot of suggestions right now, as I think the community can come up with better ideas but I think on a general level I would improve sleep grenade by maybe making it a stun instead of a sleep, make surveillance some kind of AOE, and remove the interrupt from LRM and change it to a Targeted AOE ability instead of a sniper ability, reduce the range, recharge, and add fire damage.