Both player and monster attacks need to follow the targeting rules.
If skald's armor let you redirect a hit on hit or the damage on damage you'd be fine passing those on to a target out of enemy range, but it doesn't. It affects target choice directly, and you can only choose targets and use a power if they're valid targets.
When choosing targets, the power's user must make sure that each target meets several criteria.
- The target must meet the power's target definition
- The target must be within the range or area of effect of the power
- The target must be within line of effect of the power's origin square
-- "Choosing Targets", D&D 4E Rules Compendium p. 105
This isn't "or you automatically miss", this is "or you can't use the power at all". And that's true both for the enemy melee attack and your magic item daily. You can't make them break the targeting rules any more than they can do that on their own.
So, at first pass, skald's armor looks pretty situational - only when you're in melee with two enemies who could hit each other already. However, if you're fine with just pointing the attack away from you, your options do open up a little.
It's okay, I've got my good friend Chest High Wall.
Targeting Objects
At the DM's discretion, a power that targets one or more creatures can target one or more objects, as long as the number of targets does not exceed the number specified by the power.
-- "Target Definitions", D&D 4E Rules Compendium p. 107
There's often an object next to you that an enemy can reach with a melee attack - the wall you're up against, or the floor you or your enemy is standing on. Maybe also the ceiling if this is one of those dungeon delves.
The DM can shoot this down, of course, it says so right there, but if you're going to burn an MIDaily on this you can at least give them the option.
If there's not even a valid object target next to you, though, you're a bit out of luck. Maybe you've been combo launched into exposed open space, maybe you're locked in a cursed blood duel where neither you nor your opponent can target anything else but each other. At that point, I advise just taking the L as far as skald's armor pointing an attack away from you goes, and exploring other options.