Just because I am a healing support does not mean you can skip lifesteal items, ADC
I cant substitute any kind of sustain you give your self with lifesteal. I can heal you enough to sometimes keep you alive an extra second or 2, but you need to also do your part. Whether I am Soraka, Sona, Taric, or whatever, you need lifesteal. I will try and heal you when I can, but sometimes I will run low on mana eventually, and they have CDs. Sustain from lifesteal is far more reliable and you should get it sooner than later and Doran's blade will not cut it.
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or another zeal item over it.
is a good start
for example my core build is 
if i have a healing support ill put
around...yeah....even with a healer 
) pretty much have to go IE, a zeal item, and some other damage item to be of influence. In some rough times they may go for a vamp scepter, but honestly if you have a support with good sustain, then you should be able to delay it. (not skip entirely, of coure)
What I hate way more is when people play like idiots and willingly lose half their health to land an auto or two because they think it's worth for you to spend your entire mana (or health as goat mom) on that.
