More apologies. Complications with real life have not allowed me to work on this at all.
New ETA: Monday/Tuesday. I'll try my hardest guys!

Updates to guide postponed until I get free time.
ETA: Saturday, 4/13/13, will try to finish before. Will not publish fixes until all updates (listed bellow) are added.
Reason: Busy week.
What will be in update: Updated runes/masteries. Adding "Ignite" to list of viable options for summoner spells. Removal of random color when talking about summoner spells- I did not want to have these in final guide, they slid through.

Brb downvoting that guide and any other Leona guide which doesn't have 1/13/16. Why? Because I can. -Katarina

1/17/12 is actually a variant of 1/13/16, though clearly inferior because it gives up the Explorer ward and increased starting gold for marginal improvements in defense. But any support build with 21 or more in defense is clearly wrong and instant -1.

I should point out that the highest rated Leona guide on Mobafire has 1/17/12 in utility. Not that I encourage such a mastery setup (or the one in this guide) for supports, but the mindset of there being only one correct mastery setup "omg not 0/13/17 -1" is not good since there are many different ways of efficiently building a champion in a way that works in competitive play.

The correct mastery setup for a support Leona is 1/13/16 or 0/13/17.

Though I disregard them, other DO find them viable and DO care to use them. I also, by Monday will be adding another summoner that I disregard- Ignite.

As stated above (I think), I will be adding other options for masteries.

I use this tree on Leona because I like to mitigate as much damage in lane and play as aggressively as I can. Diving by level 4/5/6+ and going in whenever I see my adc near enough and one of them in range of my zenith. Within reason of course.
I'll try using a 0/21/9 set up and I'll see if it changes how I have to play slightly, then adjust as I see fit. Leaving my original set up there just as an option. I'll also add another set with 9/21/0, as an option. Defaulting the recommended to 0/21/9, if I see it works as well/better.
Though my choices are explained, so I would like to hear your rational for why they're bad, and what I should take instead?

Fantastic constructive criticism, I bet you really helped him make his guide better with that comment. Heaven forbid you actually tell him where his points should go...

I do agree with Laggermeister on this one, utility masteries are much more rewarding as a support.

Though, all basics are explained, and the rest of the build looks decent :P
Put the summoner spells section after the combo's section, change your masteries and remove those unnecessary colours in your summoner spell explanation, and you are good to go :P

Have fun :D

As an established community member, you should be ashamed.

Because a few odd points (to you) instantly makes the guide bad.

I +1 to counter.

EDIT: Why would you put Clairvoyance, Heal and Teleport in the "other options" for summoner spells if you disregard them. Why even bother having them, and if anything, put them under not viable.