ADC build discussion

So I have done a lot of DPS calculations based on ADC builds with Bork vs IE in 2 1/2 item builds (LW basic vs Zeal calculations were included as well) and I have found that Bork loses up to ~22.5% DPS vs IE at this point. That is including the Bork passive and seems like a rather major loss in damage to give up for a bit of lifesteal and the active effect. I would really like to hear some ADC mains tell me why you go for this route over the traditional IE route.

On the flip side of things the reason I got into these calculations in the first place was to prove the inefficiency of a Lw buy after IE Zeal item vs 1 Armor item targets (or 1 armor item + tabis) when compared to picking up another Zeal. Vs a target with only Tabis you are losing ~3% dps by going LW vs a zeal item. Vs a Deadman + tabis the IE Zeal item + Zeal loses less than 1% damage compared to buying a basic LW.

While playing with these calculations I determined that many adc players build LW far too early into their build, even including the increased damage from makes no sense when buying into a team like this

https://i.gyazo.com/03ff32aeba6d3807bec1036eec9cdfbc.png

I would go so far as to say picking up a bork first item is always not worth it on champs like in competitive play, but I will cede to my relatively low knowledge in the value of an early adc powerspike compared to losing a large chunk of your dps for the next 10-15 minutes.

Please feel free to ask questions about my calculations or to try to disprove them as I am picking up adc as a secondary role and would like to refine how I approach the role.

https://i.gyazo.com/85fadd98dcd12de8d983d824c10b6fa2.png

Ashe was the Adc I used as a baseline with a standard rune page and I used the 4% attack speed in ferocity only. Blade passive calculations were done seperately from the DPS shown and is ~18.53 dps vs Varus with Lw and ~21.31 dps vs Irelia with Lw.