Although we lost our last game, you can see my points. This build works and does really well. For those who don't believe it's any good I really hope I get to play against you sometime. I want to see you QQ in the end blaming it on your teammates and how they don't help you against Sion ;)

I use a similar AD/Off-Tank build for Sion in Normal game mode. Played three games yesterday and let's just say, if I was ever alone in a lane, all 5 players of the opposing team had to gank me to kill me. Otherwise, they'd lose turrets like dominoes.

I have the summary first so that all those who don't want to go through the build in detail can just get a quick run-through of what my ideas on this build are.

Runes:
greater mark of desolation Greater Mark of Desolation x 9
Greater Seal of Resilience x 9
Greater Glyph of Shielding x 9
greater quintessence of desolation Greater Quintessence of Desolation x 3

Masteries: Standard 9 - 21 - 0
Why? We're focusing on health here, not AP.

Why AD not AP sion?
Simple. Sion can do a lot of damage either way so he'll be focused. Problem with an AP Sion is that you're so worried about getting his mana and AP up that you miss his health and he becomes somewhat squishy. With my AD build of Sion, we're focusing a lot on health because his Enrage costs health and not mana. Perfect! You hit two birds with one stone.

Do I need that much Health Regen?
Yes! At level 5, Enrage uses 14 HPs per hit. If you hit once every second that's 70HPs per 5 seconds. Can you imagine that much damage to yourself while being focused? You need something to counter all that and simple flat health won't do it alone. You'll need some regen.

Any tips or tricks?
Okay. This may cost you as a player from getting first rank in the personal score but it will definitely help your team overall. You know Cryptic Gaze? Yeah? Learn to love it! When a team member is being chased and you know you can't kill the Master Yi following you, stun him and run. Or, if you're going to attack an enemy you know you can't finish on your own, stun and let them team jump in. You won't get the kill but you'll get an assist and some reputation from your team.

Notes?
Don't comment or vote before you try this build.

First and foremost, we're building an AD/Off-Tank Sion not an AP Sion. Don't bother writing in the comments that AP Sion is better because he's not. Not for Dominion.

Everyone knows that Sion can do good damage so he'll be focused a lot of the time. Get yourself some endurance and know how to use Cryptic Gaze. Get the team involved in what you're doing and you'll find that the other team will be afraid of you and start focusing you more.

Why would you want that?
Easy. The more they focus you the less they focus your teammates and the less they're focused on the points around the map. Get the other team busy following you around as you stun them and run. Start gathering a point and when they come near, stun and run.

Ah, you think you got me, right? What if more than a team mate is chasing you and you can only stun one of them? Here's where your health and health regen come into play. They give you endurance.

I don't want to spend too much time in the introduction when we could be spending it in the juicy parts of the build. Simply said, I've tried multiple builds of an AP Sion and he sucks, in Dominion at least. AD/Off-Tank Sion has been my most enjoyable build for Dominion out of all the champs. He causes damage, has endurance and is a team player.

If those roles suit your interests, follow this build.

Notes?
Don't comment or vote before you try this build.

Runes:
greater mark of desolation Greater Mark of Desolation x 9
Greater Seal of Resilience x 9
Greater Glyph of Shielding x 9
greater quintessence of desolation Greater Quintessence of Desolation x 3

Quite standard really. Not looking for anything too special. AD and Off-Tank runes. Fits with the build.

Notes?
Don't comment or vote before you try this build.

A standard 9 - 21 - 0.

Don't need to spend much time on this. We're building an AD/Off-Tank Sion. Any extra HP and HP Regen is welcome.

Notes?
Don't comment or vote before you try this build.

In short, we're going with these items:
Berzerker's Greaves Berzerker's Greaves
Stark's Fervor
Phantom Dancer
Frozen Mallet
Force of Nature
The Black Cleaver

Attack Speed. Attack Damage. Health. Health Regen.

Sion's Enrage causes good damage and we'll have it running from minute 1 till the end of the game. Every time you hit an enemy champion, or minion, you'll be losing 6, 8, 10, 12, 14 Health Points. Not much? That's 70 HPs in 5 seconds. Add that to enemy champions focusing you. Most AP Sions will have something like 20-30 health regen per 5 seconds. You're causing more damage to yourself than that! How much more when being focused?

Made my point? You need health and you need a lot of regen. I've found that this build keeps me in the game much longer than many other builds. Just play it right. Stun and Run! You're point is to defend and interrupt captures. Believe me, you'll be able to do that.

Notes?
Don't comment or vote before you try this build.

Stun and Run! I love it. It's not about being a chicken and I'll show you why and how.

When your team's carry is being chased with almost no HP, if you stun the enemy champion who's chasing him/her, guess what? You've saved them and kept them in the game for the, otherwise, 20 seconds. It may not seem like a lot but for a game mode that is meant to finish in under 20 minutes, 20 seconds is a lot. It takes that long to capture a point.

Let's talk about capturing a point. You and your team's carry go to a point that is being defend by an enemy champion. Get in there, stun, and let the carry do the work. While the carry is killing off the enemy champion, start gathering the point. It neutralizes the turret and you and your carry get away with an extra point gathered for the team.

What about defending a point? Same story. Ping the team so they see what's happening. You'll get 3 or 4 champions coming at you, trust me. You're AD/Off-Tank Sion. They expected you to be some whimpy AP Sion. They'll come at you and perhaps you'll only stun one, but the rest of the team will back off when they see your team coming. Guess what? He's stunned and, although only for 1.5 seconds, who does every player on League of Legends go for first? The one that causes most damage? NO! The closest one to them! Yes, a problem in LoL but you can't avoid it. No one in Dominion actually "focuses" the player that needs focusing so you help them out. Stun the right champion and your team is good to go. Yes, you may die, but you defended that point.

There you have it. Saving a teammate. Gathering a point. Defending a point. With AD-Offtank Sion, you'll be dominionating in no time!

Notes?
Don't comment or vote before you try this build.

Pros
What I love about this build is pretty much everything about it. Two of Sion's skills are based on AP and two are based on AD, more or less. Your ultimate gives you extra life-steal and attack speed. Come on. How will that benefit a slow Sion with 400 AP?

"Sion, what were you doing?"
"Sorry team, waiting for my cooldowns because I'm useless otherwise."

An Off-Tank Sion means you stay in a team fight for longer and are able to defend your team. You take the hits and keep your teammates alive so they can carry the load while you respawn and buy your next items.

An AD/AP Sion means you cause damage quick and fast. Isn't that what Dominion is about? Quick bursts of team fights? You'll do that. Trust me. Sitting there in the middle of a fight waiting for your Death's Caress to cooldown, again, so you can hit everyone would have gotten you killed already. Yes, it causes a lot of damage but it takes time. In Dominion, time is something you don't have.

Cons
Two of Sion's skills are based on AP. You know what? Just look at my Pro's section. I don't think think I can add anything more here.

Notes?
Don't comment or vote before you try this build.

2011.October.03 - Added section, "Proof for Disbelievers".
2011.October.03 - Add requirement to Comment before/when Voting.
2011.October.03 - Build Created.