This deck is a tricky balancing act. I wanted twenty creatures, but I also wanted four Boros Charms and as many enchantments as possible to power Ethereal Armor. I wanted Gods Willing to protect my investments as well. Dragon Mantle is excellent at triggering heroic and powering Ethereal Armor. Hopeful Eidolon is an interesting piece of the puzzle, as it lets me keep my creature count up while adding another enchantment/potential way to trigger heroic. If I plan to cast Ethereal Armor, it's like a 2/2 lifelink, which is awesome.

Legion's Initiative was a late addition that functions something like another Boros Charm and something like a Spear of Heliod.

The creature mix was the most interesting part of building this deck for me.

I started by trying to build around the synergy between Chained to the Rocks and Ethereal Armor, but that meant I really wanted to play about seven Mountains and four Sacred Foundrys so that I would consistently have a Mountain to enchant. I started with a bunch of white creatures I wanted to play, but I realized I couldn't fit in enough Plains to support a deck that was that white heavy. My mana would have to be evenly split between Mountains and Plains, so if I wanted to reliably be able to cast two creatures on turn 2, I'd need to play a roughly even mix of red and white creatures. Fortunately, the red creatures were about as good as the white creatures I wanted to play, and I was able to balance them smoothly, which explains some of the weird numbers.

After playing the deck some, I found that Chained to the Rocks really hurt against control decks and moved them to the sideboard, but I still considered them an important part of the deck and stuck with the mana base that supports them, which had actually worked surprisingly well for me.

Wojek Halberdiers was a late addition that came with the Legion's Initiative, but I've been satisfied with it. It's only barely worse than Akroan Hoplite.

Fiendslayer Paladin is another important part of the sideboard since against red decks the deck naturally has a large number of enchantments to put on it. It's a very easy way to steal wins.

Akroan Crusader is a little weak. But there are some matchups where making blockers is important, and it generally plays well with Akroan Hoplite. I started with more of it, and that was too many 1/1s. It's very bad to draw two, but I like having it in the deck as early heroic option.

http://www.starcitygames.com/article/27090_Building-A-Hero.html