I've added Annie to ''But what about these champions?'', together with my opion.
I've added more runes and masteries along with explanations and clearified building 40% CDR.

About Blitzcrank: he can sure get tanky but he isn't a frontliner like Thresh, he can initiate but won't actually go in. He stays next to his adc mostly to peel with Power Fist or cancel channels ( Death Lotus etc). I therefore feel that 21 in utility gives him a lot more then 21 in defense.

Thanks for the feedback!

no Annie :(

I feel like this guide is pretty detailed at some points, but for other things it just doesn't have a lot of options.

Runes: greater mark of hybrid penetration can be really good for most supports, specially Lulu or Sona. And you only lose few magic penetration for the amount of amor pen you get.
- Having some Greater Glyph of Mana Regeneration is awesome for supports that have heal/shield, you can spam them a bit more so your ADC will always have more health.
- quints of speed are certainly good, but if you are an initiator like Leona or Braum, Greater Quintessence of Armor helps a lot surviving it.

Masteries: hmm, I think it would be better if you showed an image or detailed better which masteries to take, if someone is trying to get out of low elo, chances are they aren't that sure about which masteries are the best. Blitzcrank not a tank support? He is a beast as tank and also has quite some damage, I like going with defense masteries with him.

Items: I don't think I will ALWAYS want to have 40% CDR. For example, if the enemy ADC is becoming a beast, I will build Thornmail and Randuin's Omen first. Or if there are too many assassins/stun I will go for Mikael's Blessing.

These are some stuff I've noted so far, good luck with your guide.