NO. If the sightstone was that good as many claim, there would be NO good reason to not buy it on EVERY champion. People who turns aggressive against a support with no sightstone should just buy one.
Vision is GREAT, don't get me wrong, I buy asap a 
on every champion I play no matter the position and make sure I use is as often as i can. However.
-
There is other way to gain knowledge of you opponent position. You can apply a sane pressure on your lane so your opponent at least have to stay at his lane. You can predict better the movement of the opponent based on the information you had.
-
There is a cost linked to leaving your lane to ward anything else then the bush in the river (which could be covered by level 1 trinkets). You lose exp, you lose gold, you lose pressure. Again, i'm not saying it's bad, I'm just saying you can't hope to make anything close to 75g ward per minute without also expecting your adc to have to pop a hp pot or two every time you leave him like this.
-
There is several case where a well chosen core item on a support is superior then the ward and hp generated by the sightstone.
Why people swear sightstone is so good is a matter of visibility. Wards are visible you can see and feel how much they gave you, 100% mana regen, not so much. And that's what cause a sever bias toward flashy items and summoners spell.
TL;DR: If you think the ss is SO good no support could possibly think about another item, well you have to explain to me how the hell it's not the case for the mid laner ? The mid laners is in the middle of the map, he have to roam twice less to make a proper use of all those wards. Why wouldn't they have one if it's so good ?
isn't a necessary buy because of his W vision.
, cause of her plants.
if you actually care about your ADC and team. 
Bones