Comments about powers:
Striker Bonus Damage (or lack thereof)
Unlike the strikers in the PHB, your class does not have any sort of striker bonus damage ability, like Sneak Attack, Hunter's Quarry, or Warlock's Curse. To fit with the concept of the class, I would suggest something like Sneak Attack-level bonus damage (2d6/3d6/5d6, with options to increase via feats and class options) to any target that you hit with an attack that you had grabbed before the attack. If you do this you could also include an at-will that grabs (say Strength vs. Reflex, 1[W] damage plus target is grabbed) so that players will have a chance to get the bonus damage without having to spend an entire standard action doing nothing but grabbing. An at-will grab woult also make Martialist a more unique class.
Implements of Doom (IoDs)
The Implements of Doom seem underpowered, especially for a striker, as they have lower proficiency and damage values than most melee weapons. There may be ways to increase them via feats and class selections, but there is too little information to tell. That might be what you're looking for - a striker focused less on damage and more on immobilization and pumping out conditions (i.e. sort of a controllery striker) but this is something to look at.
EDIT: Now that I think of it, this might not be bad. The fact that so many of your powers target NADs may provide compensation for the lower weapon damage and chance to hit.
Weapon Keyword
It's unclear what the point of the Weapon keyword is. You're not using weapons, you're using IoDs. And the definition of the Weapon keyword is just a copy of the definition for the Fist keyword. (Note that if this is going to be a GSL product, you're not allowed to redefine existing keywords. Even if it isn't, I don't see any reason to since it's just going to cause confusion.)
Reliable Powers (or lack thereof)
In general, daily powers that have only one target and no miss effect are given the Reliable keyword, so that they are not completely wasted because of one bad roll. It might be a good idea to consider goving the Reliable keyword to some of your dailies with that effect.
Specific Powers
Weaponless Does Not Equal Weak and Attack to Defend
WDNEW seems strictly less powerful than ATD. ATD is usually more likely to hit (most monster ACs are at least 1-2 points above their Fortitude defenses) plus ATD has an additional special effect (which happens even on a miss.) I don't see any reason to take WDNEW.
Forceful Shove
Do you need the restriction on size categories? Most forced movement powers don't have it.
Dance of Death
I think there's a misprint here. Why does the attribute used for damage bonuses change at 21st level?
Redirect his Effort
Could use more clarity w/r/t the phrase "just prior." If a Warlock moves into melee, then uses his minor action to curse the Martialist, then attacks, does that count as moving "just prior" because there was a minor action in between? (Okay, I know PCs aren't supposed to be fighting each other, but that was just an example.) What if a monster moves into melee range (non-charge), provoking an OA from the fighter (which misses), and then the monster attacks? What if the monster moves into range, then readies an action to attack on something that triggers almost immediately?
Suggestion:
(1) Make the ability only activate when the Martialist is charged.
(2) Reword it as something like "if the creature moved more than one space since the beginning of its current turn (or most recent turn, if not attacking on its own turn)" The "more than one space" is to avoid RHE triggering when all the creature is doing is making short moves to slide into position, which is probably not what was intended.
Vault
I don't believe that monsters generally have listed heights.
Quick Jab
This power needs a complete rewrite.
The "bonus to initiative roll for one action" is a mechanic unique in the game, and it's not totally clear what it means. My interpretation of it would mean that if the Martialist is at initiative 17, and a monster is at initiative 18, then at initiative count 19 (before the monster acts) the Martialist can preempt him with the Quick Jab, then the monster acts (at IC 18) and then the player does his move and minor actions (at IC 17). However this severely limits the ability, because it means it is only useful if you are within 2 initiative points of the monster you want to preempt.
Second, the attack is extremely weak (weaker even than at at-will!) and has no side effects, so even the pre-emption would only be useful if you happen to knock the target down to zero hit points with the attack.
Suggested Rewrite to make the power more useful and stick to the apparently intended use of pre-empting an opponent's action:
Quick Jab
Daily • Martial, Fist (Weak Hand)
Immediate Interrupt - Melee
Trigger: A creature adjacent to you makes an attack.
Target: The attacking creature
Attack: Strength vs. AC
Hit: 1[W] damage, and the target is stunned until the beginning of his next turn.
Miss: 1[W] damage, and the target is not stunned.
Crack my Knuckles and Stomp it Out
These abilities seem very weak. Only 1d4 extra damage? Maybe up it to 1d8 or even a bit more.
Bat from the Air
This could even be upped to a +4 (compare Shield (Wizard Utility 2))
Block the Attack
You might want to change "-2 penalty against melee attacks from all other creatures" to "grant combat advantage to all creatures making melee attacks against you" to make it more clear and take advantage of an existing mechanic.
Constraining Chop
3[W] seems like a lot for a 3rd level encounter power. Maybe reduce to 2[W]?
Leaping Blow
I assume you have to make a Jump check to get into the square. If you don't roll high enough to get in range what happens? Is the ability wasted? Also do you get a running start on your jump check?
Overpowering Rush
Suggested changes for clarity:
Replace "you bull rush the target" with "you push the target one square."
Move the indented "secondary attack" line and the "hit" line under it to between the main "hit" and "miss" lines, and add "and no secondary attack" to the miss line.
Quick Strike
See my comments under "Quick Jab."
