Now that you've got an idea of what he's able to do, let's dig into it a little.
Cho'Gall is the first Ogre-Magi, he's powerfull, corrupted and a little dumb and mad (it depends on which head tbh).
The 3 spells from Warcraft II look like something an agressive Support would have, but he seems more fitted to be a Mage, and still, his Runes seems great for pushing. With this in mind, I decided to go the Specialist route, and mix things a little.
(Trait) Corrupted Orb is what's makin Cho'Gall a good pusher. Darkened Creations aren't that big of a threat, but since they automatically spawn and they're untargetable, they push the lane no matter what, as long as Cho'Gall is around.
Consume Darkness is a must-have talent if you want a good sustain in lane, at the cost of your pushing ability though, so be careful.
Empowered Corruption and Fast Shadows increase your pushing ability even more, but since Darkened Creations aren't THAT great in teamfights, you'll have to choose carefully (remember that dead heroes spawn Darkened Creations too though).
Liquid Corruption can be great for a mass movement speed reduction on the enemy team, specially coupled with Corrupting Adherent.
(Q) Eyes of Kilrogg was a nice but weird ability in Warcraft II that allowed the player to control a fast moving eye that revealed his surroundings, granting map awareness. Obviously it wouldn't fit HoTS gameplay as it is, so I had to make a few changes.
The Eyes will travel fast and at random in a long distance, so you'll have to orientate the cone wisely where you want to see things. They might missed the enemy heroes, but they'll cover a bunch of terrain.
As for the talents, you'll be able to improve the vision and duration, which is nice on bigger maps, make them spawn Darkened Creations that will pursue heroes, preventing them to mount for a few seconds (good on maps that require to gather quickly : Punishers and Tributes I'm looking at you), or make them cover the map with Runes, which could be awesome to soften your enemy's team, kill some fleeing heroes or reveal stealth.
(W) Ogre-Magi's Bloodlust Sadly for me, Bloodlust already exists, but it's a team buff, not a single target one, so I decided to go with this anyway. This ability is a burst buff that also allows the user to flee and/or chase, but it has a very long CD, use it wisely.
If you want to be a good support for your team, you can improve the duration and healing effects on Bloodlust, it's especially good on Illidan, Butcher, Leoric and other hard hitters with good sustain.
Frightening Presence will make the targets of the Bloodlust user Vulnerable, allowing some fun melting down with the right teammates.
Mob's Frenzy will be awesome with a pusher build, if the enemy team lets you alone in a lane, their forts will get destroyed in a matter of seconds.
(E) Runes is your only non-ultimate damaging ability, but is not a skillshot or a targetable ability. It's best casts in bushes, in small paths, in base entrance to protect your Abathur from being killed by Nova/Zeratul, or beneath minions and/or gates, to allow some good pushing/damaging structures (when minions step on it).
Corrosive Runes and Large Runes are perfect for this last part, as it melts structures and minions (like Tychus' grenade) in a large area, but you could also take Psychic Runes for more sustain in lane or Blood Written Runes if you want to cover the map and use them as traps.
Volatile Runes is your only way to burst down heroes, but necessitate some planing beforehand.
(R1) Corrupting Adherent is the best ultimate if you want to push hard. Unlike Darkened Creations, they can be targeted and killed, but they have a fair amount of HP (maybe too much ?), good damage, are great against minions and structure, and benefits from Darkened Creations talents. If you take this, you're at least as scary as Azmodan if your enemy team ignores you for a moment.
If you take Corrupt Everything, you can even leave the lane, it will be pushed really fast by your passive, forcing your enemy to split if they don't want to loose their Nexus in a matter of minutes.
(R2) Corrupting Crash is meant to break your enemy team's formation, much like Raid Boss do. If the front line stay still and take some moderate damage, their back line will suffer a lot more. Casting that on a lane will also clean it all the way, allowing some nice push capacity.
If you take Corrupt Minds, the enemy team will need to be even more cautious, as it will empower both the ultimate damage and your teammates burst capability. The best way for them to avoid that, is to lure you to cast it, while waiting for the effect of Bloodlust to wear off.
Heroes of the Storm Build Guides
Both Cho'Gall's heads would be pleased with some feedback though, ahah.