You were the one in charge of balancing out Arena and Siege?
My first check would to be make sure all skills actually follow LoS
Balance out Chiron Damage in Siege War so that it doesn't bypass defense, also that hits on chiron aren't bypassed either
Bring Bleeds back to siege at 1-10% of the damage they were doing pre-ChV (would require balancing)
Take Immune foods and Pheonix Redemptions out of PvP
Make it so Tornado (Herald Skill) doesn't immediatly go on Cooldown if you don't finish the cast or atleast make it so the cast is interruptable only by lightning towers I guess there's no reason that flame towers should interrupt it's damage.
Take away the beneficial status of Fearless so that it doesn't get removed by R/M or S/W
Give Herald the ability to do more than use normal attacks during the duration of Fearless
Change the functionality of Shadow Prison during Siege
Lower the amount of damage done in Siegewar along with heals so that damage was 10% and heals were about 20% approximately
Fix the functionality of Siege Weaponry
Fix Mage Absorb so that Flame Tower damage goes through the absorb or it doesn't but still fears them
Change the Rogue skill Hide to the way it functioned pre-Ch5 patch, also possibly add a 2s CD not that it really would matter, also Fix Vanish so that it removes you from Combat 100% of the time, possibly make it so vanish auto triggers hide
Change the way projectiles function in general, if a projectile is launched it should always hit it's target regardless of it the character who sent the projectile is dead
There's probably more that I would fix, I would probably make Iceblade a projectile as well as some who may look at this topic may have a sneaking suspicion about.
I just thought it'd be an interesting discussion, sort of a "if you were in charge of the world" kind of thing or what have you.