##Dual wielding
You don't for several reasons. Lets go over your first issue, dual wielding identical weapons. This serves no practical purpose. You can't strike at a target twice at the same time. Your weapons would clash so you're alternating. Now the speed increase between two identical weapons and a single one is small. Both using a single weapon or using different weapons would have an advantage here.

A single weapon would be lighter or could be made bigger, increasing the distance between you and the enemy weapon. Two different weapons would give you a greater flexibility. For example an axe to hook a shield and a sword to exploit the opening. Likely one of them would be used more defensively. 

Because that's the thing. Why would you not use a shield? only if you wear sufficient armor to negate the need for it. But then why not opt for a bigger longer weapon and engage the enemy from a greater distance?

Dual wielding isn't practical. You can't aim and in melee its disadvantages outweight it's advantages. So that's your first problem with warglaives.
##Weight
Now if we ignore that we get to the second problem, weight. They're indeed heavy. You're only utilizing half the weight for reach because you grip your weapon in the middle. I'm sitting here unable to recall any melee weapon that extends an arm's length in both ways.

A quarterstaff wasn't wielded in the middle spinning around. Sure there was generally one hand in the middle but the other would be more towards one end. Your hands continuously shift along the shaft. Extending the weapon towards your enemy. It's held in front, strike at the enemy, swipe at his feet.

So what kind of attacks could a warglaive do a sword can't? They look like a double scimitar to me. I would even argue the curved blades make using the underswing of the wrist even harder to use. It has limited mobility to begin with.

As you mentioned yourself, weight means momentum. I'd say you're better off wielding sucha  heavy blade like an axe. Each swing swirls into the next. You don't just start an attack, you keep them flowing. That on the other hands kida requires you to have another way to block. Something like a shield would work nicely. 

##What works
So not to be a total downer, what can we get to work? Modern materials allow for a great deal of light materials. Aluminium with a harder edge? I'm not a smith or metallurgist but I'm sure modern material can reduce the weight.

Second thing I like is the handguard. It's basically a buckler. A small one but scale it up to the size of a dinner plate and it would serve you well. Now bucklers have been used offensively. A sharp metal rim gives it a mean punch if you strike with the edge forward. The curve even limits the contact point. Alternatively bucklers have been wielded with a [dagger gripped in the same hand][1]. Allows for a stab if your defensive hand manages to spot an opening.
[![Yes this is a targe, same technique applies here, grip is a grip][2]][2]
##My design
Make one buckler with short blades, one going up, one going down. Alternatively go for a broad push dagger on the knuckles. Either way, knives with a small shield. 

In your other hand is your main weapon. This can really be anything from a sword to an axe to a mace. If you want to keep somewhat close to a dual blades weapon you swing around wildly, go for almost straight blades, like a katana.

Alternatively I guess you could made a dual tipped spear and a buckler/glove hybrid on your middle hand. Not sure how effective such a setup would be.


  [1]: https://www.youtube.com/watch?v=EQ1q-IfLDdo
  [2]: https://i.sstatic.net/tZfMY.jpg