Yes, unfortunately, deaths cost you greatly. One of the support's jobs (in my opinion) is to trade his life for a carries if needed/possible. That being said it's not supposed to be willy nilly. However, if someone should be dying, it should be the low income champion.
It almost discourages that sort of behavior which might lead to your carry dying a few times more which can really make or break the game. However, it does encourage you and your ADC in laning phase to be a lot less risky so you're not forced to make the choice of you or the ADC taking the express lane back to fountain.
On the reverse, warding DOES also account for a hefty chunk of your grade. So many ADCs do not ward at all (or simply drop one early). I've never seen an ADC get an S rank if they are not warding even if they go 15/0/15.
Ward up, play safe-ish, and have a great game. :)