Well, MF Nunu is different, Nunu + (insert thing here) is a special exception because of his ridiculousness haha :x MF Nunu is kind of absurd and do synergise better than most bot lanes, you're right (my last normal was vs. MF Nunu, in fact). When I say she's bad with stuff like Soraka I just mean anything that doesn't actively boost her power or aggress. Sorry for the wording! Nunu is reactive but not in the sense that Soraka is reactive, because Nunu (saying this as someone who fucking hates Nunu) lends himself really well to aggression. Armour buff or no buff, I don't think Soraka lends herself to aggression, just to countering it.
I think Corki Soraka is fine, but I also agree with you, I do not like Soraka with lane bullies (I don't like Soraka much in general, although I think she has her uses!). If you want a heal and a lane bully play (Sona/Nami). But I still think Corki Soraka is an acceptable lane, it's not like MF Soraka where Soraka is totally wasted. Soraka offers no CC (except silence which ehhh other stuff locks you down lol), no (damage) steroid, but at least Corki and Soraka do synergise, unlike MF and Soraka.
New World Order: Yes, Lux's shield is, if I recall correctly, the best shield in the game (when it hits). Omicron specifically said 'AD boosting shield'. Janna is basically a free BF Sword for your AD Carry. Press E, win trades. Lux shield is not a steroid which is specifically what is referred to by 'AD boosting shield'. It's only one of those things. Perhaps I'm wrong and Omicron was actually suggesting that Lux's shield doesn't shield for as much as Janna's, in which case he would be incorrect. It's worth noting that you don't necessarily max shield first on support Lux, unlike Janna, in which case it is weaker in lane. What sets Lux apart from other supports with a shield is the immense amount of early damage, both burst and poke, that she provides from an extremely safe range early on. If you walk into Light Binding, you're screwed. Maxing Lucent Singularity first lets you actually make use of what makes support Lux different to the others.
Also, wrt: support Zyra -- Yeti is correct. Good supports have utility without farm. This means they scale past lane without farm/items. Support Zyra does a huge amount of damage in lane, but since you're not going to get items, you'll quickly get outscaled. This is true with every single support, since you shouldn't be building damage; you should be building items that will give your team utility. Once you get out of lane, yes, support Zyra becomes a CC bot, as does basically any other support who didn't grab a Mejai's Soulstealer after a triple kill (note: don't). That's just the reality of playing support! You don't get gold, you don't get items, you don't do the damages and get kills. You are there to protect your team and make plays. :) Make the most of your base values while they last.