I don't make my living off this game but I think I can help a little.

Stacking auras is somewhat of a waste of money. Yes you can technically benefit from an aura twice, but it won't come out as strong as say, one person getting Will of The Ancients and the other getting Abyssal Scepter, but neither getting both. The gold is better spent on other items, especially on your AP and AD carry. They need to fill their slots with big, expensive, items so they can squeeze the most power out of their build. You have some good picks in here though. Soul Shroud is great on a support. Aegis of The Legion is awesome for someone on your team to pick up. Stark's fervor is okay on carries but a lot of the builds tend to avoid it. Will of The Ancients is a good choice on Fiddle. Abyssal Scepter is good on a support or AP. When all those aura's come together it makes your team much more buff in a 5v5 encounter, but that's where the value comes from. Five buffs for the price of one. Not five buffs for the price of two.

As far as team building.

The setup that is widely considered the strongest is as follows:

Tank
Off-Tank
AD Carry (Often Ranged)
AP Carry
Support

"That 5th Wheel" isn't really a class, and Zilean is a support.

In this setup either the tank or the off-tank will jungle, leaving the other to solo top, the AP will go mid, and the support babysits the carry in bottom, essentially giving each person their own lane to farm (except the support, who, in many cases, gets gp5 items and doesn't farm much).

Your setup would be better if you removed Zilean or Sona in favor of a jungle like Warwick, Udyr, etc. Alternatively Rammus can jungle and you could get a solid off tank like Garen, Jax, or Cho'Gath.

Runes and Masteries are easy to find. If you are trying to make a guide to show a strong team setup and not going into detail for each champion, simply copy one of the top guide's and be sure to credit the author of that guide at the top. Many other high rated team guides do this. Emphasis on credit the author.

Guardian Angel. It's not that awesome. Again, I'm not a pro, or probably even good at the game, but I get guardian angel only in specific situations. I get it sometimes as the last item for a tank build, if you are losing the fight horribly, it won't help you, but if you die and lasted long enough for your team's DPS to ruin their team.. Hey! you get back up and have one less death. It's okay on other classes but if they stomp you once late enough in the game that you have bothered to get GA, they will probably stomp you again when you have 750 HP, which is a pittance in the late game. The defensive stats are decent but the money is better spent elsewhere. You mention Thornmail's stats as being lower, disregarding the passive and that it's about 25% cheaper. Also taking anyone by surprise with Guardian Angel is extremely uncommon, as it puts a swirly white aura on your champion when it is off cooldown.

I hope some of this helps. I'm not going to vote because you said it's a work in progress and you're open to suggestions.

Are you new to this game?