1:require comment to vote
2: if your going to play defensively, get Block in masteries
3: try and clean up the pro's/cons section, I like the pros and cons, but it looks sloppy when its out of sync.
4: consider a Rod of Ages early, as you wont have any tankyness and you will be lacking in damage until you finish your Archangel's Staff and move on to more tanky items

Other then that, guide looks good

@lazysushi Thank you so much! I did what you suggested and it helps a lot. I'm able to burst more without worrying so much on my mana. :)

"spell vamp is wasted because all her abilites (ultimate excluded) are AOE."

biggest lie ever. Spellwamp scales BETTER with aoe. Yes, it does only get 1/3 of the effect but remember that you hit multiple targets. If u hit 3 targets with an AOE spell u heal for the same percentage as if it was a single target spell. The great with spellwamp and AOE is that you can often hit more then 3 target, thus healing for MORE then you would with a single target spell.

To the author:

Don't build thornmail. build Frozen heart instead. with the passive it reduces more dmg then what a thornmail does. Frozen heart also got mana and cdr so maybe switch the Boots to Merc treads or boots of swiftness
Edit: don't build archangel staff that late. it takes at least 20-30 minutes to stack to an amount where it's worth it. Build goddes tear first or skip the item

Thanks for the reply. :) I changed the Pro/Con. From what I've played of Syndra, she takes a lot of damage from both AP and AD champions and EVERYONE loves to target her. She's kind of broken in a way. Yes, she can be a glass-cannon but I found out it feeds the enemy kills a lot faster that way even with the max range. I do play her at max ranged but she can still be caught by snare's/stuns and killed very easily if someone is ganking your lane. She also has enough damage as is in the beginning to start out with. You don't have to have both armors to weaken your AP. I just play her like I play Vladimir minus all the the health regen. It works for me because she feels like she's a lot like Vladimir.

I also don't see where I mentioned any spell vamp items. I've seen others use spell vamp on her but I haven't used it once, only magic penetration. Especially if they're building magic resist against you or some other buddies.

I was able to get kills/sustain my lane this way with this build. It works for me but it probably won't work for everyone. I just wanted to add my build because it might help other people too even if they're having a lot of trouble building her glass-cannon.

There are many things I do not like about your guide. The first of which are the Pros. These are supposed to be specific to that champion... you say she has more armor late game? Thats only if you build armor items. 2nd Her lane sustain is also poor - unless u grab an early chalice. spell vamp is wasted because all her abilites (ultimate excluded) are AOE. 3rd I agree that she benefits from CDR however, you do not need it to get 3 orbs on the field. This is how. Cast Q then after it comes off CD recast Q and grab your first orb with W. Wait for Q to come of CD or almost and recast W. 3 orbs on the field. You have this for about 1-2seconds before the first one disintegrates.
4th. Counter champions. LeBlanc = No. Teemo = No. These 2 are very easy for you because of your amazing range. In fact syndra is good against virtually any squishy target you can think of. (why would teemos blind be and issue for you? all your damage comes from your abilities.

In my opinion Syndra is a glass cannon - played at max range. causes hell to team fights. She doest need to build defense because if she maintains correct positioning she shouldnt really be in a position to take that much damage!