Run health quints, and against kill lanes, max W (you'll win lane 9 out of 10 times simply because the strongest kill lane supports are melee). Sona is actually one of the tankier supports in this game if you choose so (and is basically by far the tankiest support lategame after Alistar), and that is why Riot specifically nerfed her base health. Also Sona is a much stronger teamfighter than Zyra factoring a gold starved build and can carry games with basically a Philo and Chalice. Sure Lulu is slightly more useful than Sona lategame, but Sona simply dominates the laning phase if you know what you're doing, and also shines in teamfights pretty well.
hmm I cannot disagree more here. There are tons of support that are way more tankier than sona. Taric, Nunu, Alistair, and yes even lulu.
All stat here are at 18:
Sona: 1600 hp 65.4 armour 30 mr w aura is 15 armour mr or 35 armour mr for 3 sec after skill use
Lulu: 1891 hp 75.6 armour 30 mr shield and ult obv but since the skill is usualy not used on herself it dun count
Taric: 2088hp 74.1 armour 52.5mr w gives 60 armour while off cd and 30 while on cd
Nunu: 2381hp 79.5 armour 52.5mr
Leona: 1996hp 73.8armour 52.5 mr her w gives her 70 armour and mr for duration of the buff
Janna: 1760 hp 77.4 armour 30 mr
In conclusion sona is tankier than janna, and sorka (if soraka does not heal herself and sona has the w buff on), but that is about it, and this is only contingent on sona having the w up instead of other buffs. If she does not have w up Sona is the least tanky support there is. If your argument brings items then most support build simmilar items, except like zyra going ap support. If your argument counts in how many heal she can use in team fight, then this is true since sona can pull off at least 2 + in most teamfight giving her effectively at least 240 hp or more, but that still makes her way less tanky that most beefy support that I mentioned top.
In terms of lanening she really is not that dominant lol and like i mentioned in my post supports like lulu and zyra just flat out outrange her in harass. She does have sustain going for her, but remember that is mana that you could have spent damaging enemy going into heal, and sona's heal is not that mana efficient. (80 mana / 120 heal at max while lulu does 260 dmg for the cost of 80 mana for example)
She is still great in lane, but support like Lulu and Zyra can easily stand in par with her in lane.