You could also sell your philo stone after getting your use out of it, and grab something else to assist your team with. I'm not saying Shurelya's is bad, i'm just saying it's not good for Leona.

I like your use of use items, they mean your pro

First off I do get aegis before shurelya's, so she IS extremely tanky at the point in which I buy it especially with W up. You need to take into account the PRICE of shurelya's before you say its bad. Yes, it isn't as good as any of thoose items you listed, but seeing as I already got a philo stone it is only 1400g, for that price you get 15% cdr, 330 health, and the active. Not saying its better than another item, just that its the most cost efficient step forward at the point in the build where I take it.

List of tanky aura items:
Abyssal Scepter
Aegis of the Legion
Frozen Heart
Randuin's Omen
Soul Shroud
All of these items (yes, even soul shroud) would be better suited for Leona than Shurelya's. Frozen Heart and Soul Shroud mixed with Elixir would cap your cdr. Aegis would give you an amazing amount of tankiness, while also tanking your team up and giving a small damage boost. Frozen Heart just ruins enemy dps champions, which is the new metagame for low-mid elo. Randuins Omen gives a slow upon being hit, which would give a somewhat similar effect to Shurelya's active. Abyssal scepter gives your mages a small kick in damage against enemies.
So, tell me why, again, do you pick Shurelya's over these items?

Thorough, well out, The Reverie item is necessarily +1

I don't quite understand how shurelya's is useless... first off, it gives health. Health is "tanky" at the point in the game when you get it your armor/Magic resist is high enough that health is worth getting. Furthermore, the fact that you would build her with only "tanky" items is silly. A tank's only job isn't to be "tanky" they also have to be able to Support their team. Shurelya's accomplishses this in two ways, CDR which Leona sucks without, and a sick active that I gaurentee will save a life or get a kill at least once per game. Not to mention that building this item allows you to get an early philosopher's stone.

Shurelya's is useless on Leona. you could get something more tanky instead.

As a first time post this is well done. more people should follow this build.

Very well put.