Hey I just wanna add something to what u said.

Soraka is no good as a carry xD but Sona is, even getting a random Lich Bane late game or damn even just a Sheen would be fine. I played her once trying to play as a support but since it was one of my first times supporting with her I didn't realize her crazy damage and got a double kill and 2 assists immediately haha. DOn't underestimate ur passive or Q xP

Thank you both for your comments :)

Halipupu: I forgot to check CDR, which is my fault and I will address that issue the next time that I sit down to edit this. Thank you. :)
Regarding 15% Mpen: I typically play Sona less aggressively, especially since my build as is has 0 AP. This means Q is dealing up to 250 at rank 5, so the only really magic damage you'll be dealing is in your ult and chords. But really, your ult will deal 350 damage by 18, since this build again calls for no AP. Chords will deal 23 - 176 damage without Q, which is up to about 352 if i'm right. This is certainly a lot of damage, but you'd be more likely to pick up a kill/assist if you used E for the 25% slow anyway. The utility of E's chord exceeds that of Q's in most scenarios. I know Sona deals magic damage, but really not enough to make that point in AK worth it. For a support like Soraka, I would agree that AK is a good idea, because with AK Soraka can now be a semi-efficient AP carry.

I don't like W's chord as much as the other two because I think E greatly overshadows it. I would expect my teammates to be more likely to escape Brand if he was slowed more than if he was debuffed. Placing a slow on a strong DPS champ or burst damage champ gives my team room to either turn it around or to get out of range. Because Brand especially can deal massive amounts of damage as soon as you get hit by the start of his combo, it's better to escape/never get in range than to nerf his in-range damage.

I apologize for the lack of color in the guide, also, as at the time of writing I didn't know how important it was. I will edit this again when I have the time, adding color and likely BBCode, as well as other revisions. Thank you both once again! :)

Ok, I'm going to point out some mistakes in the guide: you have mana seals, not mana regen though you mention in the guide that mana regen. If you meant mana regen, then that is ok, but if you really mean mana runes, then that is bad, because mana regen is far better. Second is that you don't need that much CDR, you exceed max 40% cdr quite heavily. Masteries give you 9% + runes 14,5 % = 23,5 % from those already. Therefore getting CDR shoes will give you 38,5% which is nearly max cooldown reduction. GEtting 30% more CDR from items will end up you wasting more than 25% CDR which is a lot.
So, I suggest you build different shoes (maybe Mercury's Treads) OR skip Soul Shroud/Shurelya's Reverie and build something else in place of either one of those items, and take some other quintessences to max her efficiency.

Also, I think you should take 15% magic penetration from masteries, because she DOES have magic damage. In fact she has one of the best damage as supports: her Hymn of Valor does great damage to 2 targets, her ulti has nice dmg and all of her power chords do awesome damage. I like how you explain when to use them, W power chord truly seems like it's good for nothing but it can save your allies life if you cast in on some aoe dmg dealer like Brand who will do 20% less dmg.
You're skilling order is quite weird, but original :)

Last, you really need to put color in your guide and explain teamwork and such far better than with just a few words. I'm not voting yet, because I want to give you a chance to improve this guide :) I hope to give this guide +1 someday, but as it is now, imo this is not a complete guide.

I really liked it. Short but informative. Try to add some images and colors into it when u can, it makes it look more appealing to the eye. Very gj tho. I like the idea of taking both charms at first :)