Arms is all about burst damage, so increasing Lion's Fang's damage for the burst window is key. The default Banner, and most of the time the ONLY Banner, for Arms is Banner of Dalaran. Therefore the increased Slow also helps keep up with your Colossus Smash target to execute the full combo. The Heroic Strike damage is just a bonus in the burst window, and should always be ready for that first Basic Attack after Colossus Smash. I just find Overpower lacking behind the other two Talent...

I just got an interesting idea from your suggestion of Multiclass... Let us see if it works...

Not sure how long the range will be for the Trait, but I can surely tune down its power. Looking back at it, I agree that it is way too strong. As for Outbreak, I thought a little bit of randomness would eventually make its way to the Nexus however I think I have something to replace it that keeps the same feel without the randomness you mention.

So Zoltun's Trait is nearly identical to Leoric's?

I would switch out Victory Rush for Second Wind at Level 7 - provides more self-healing with the Twin Blades of Fury build.

Updated November 26th.

I did not catch that, thanks for letting me know! Endurance will definitely have to be reworked. I wanted to reward a well-placed Headbutt, but I agree that the Stun duration is too high and needs to be lowered. I might even change the Stun to a Slow instead... Thanks for the feedback!

You would not have to make the Surge of Darkness / Surge of Light available at Level 1. I was thinking either Level 16 or 20. Yeah, that would probably be better. I thought pure healing rather than damage would fit the theme better, at least for Light Vortex. Alright, that is actually cool. Raises the skill cap of the Hero a bit to get a lot of burst damage on multiple Heroes or pull off a huge heal on yourself. Oh okay. Yeah, that makes a lot more sense.

I like this Concept. You give the Twins a unique feel with only one active at a time and the player switching between the two rather than both active at the same time almost too similar to The Lost Vikings. I do have a concern regarding Shield of Darkness / Shield of Light: it looks a little lack-luster. Both are the same Ability with no real consequence depending on which Val'kyr is active. Perhaps instead of giving a flat Shield, instead of Shield of Darkness reduce Attack Damage taken...

I toyed around with the Heroics, mainly Hysteria, for awhile before deciding upon those iterations. I originally felt Hysteria was too weak compared to a new form of crowd control when Hysteria only affected Minions. I added on captured Mercenaries and Heroes while also increasing the duration. However, it shows that Hysteria is always the go-to choice for Varimathras as an unbreakable (unless Cleansed) 3 second charm effect that can affect multiple Heroes is much stronger than a 4 second...