Tanks need a way to apply grievous wouds too
Tanks have Thornmial, which is way better vs. lifesteal that Grevious Wounds ever was.
These item combo will allow the adc to basically out-tank the tanks
Only if the tank in question does no damage, that build is very AD+Life steal heavy and ignores a lot of secondary and tertiary AA damage multipliers like critical strikes, armor penetration, and to a certain extent attack speed. You'd need a solid ~20 seconds of uninterupted auto-attacking to kill most tanks with that build. Which is a fairly long time, especially seeing as tanky DPS champions like Nasus need about 2.4 seconds to kill a squish.
Due to AA stats scaling in a 2x2x2x2x2=32 fashion, focusing on AD almost exclusively with such a build will make an AA focused champion completely useless vs. anything but a low-damage damage-sponge as well, as an AD life-steal build is largely opperating in a 2+2+2+2+2=10 realm.
Also, all life-steal is based on the amount of damage done.
Armor reduces the amount of damage done.
Doing 300 damage vs. 0 armor with 45% life steal means 135 HP restored per hit.
Doing 300 damage vs. 300 armor with 45% life-steal means you're only doing 75 damage per hit and restoring 33 life per hit.
Of that 300 armor, only 135 of that needs to be bonus armor for Thornmail's 25% of total armor damage to completely negate that life-steal, and that's before calculating the 15% damage reflection.
With 300 armor total and a full 90 of that being base armor (worst case scenario as that's the highest base armor in the game), you're also reflecting 97.25 damage (or 74.8 after 30 MR) where 300 damage per-hit is doing 75 damage with 33 life steal in that listed full life-steal build.
A squishy taking 42 damage every time they deal 75 damage is also really bad for the squishy because they're squishy, a tank will generally have a significant health lead. In this case: a tank would only need 78.5% more HP than the pure glass squishy to win via an AFK kill, assuming the tank in question has no noteworthy sustain.
Most tanks also have a base 1000 damage in their QWER combo, have pretty impressive base AD for un-itemized auto-attacks to do something late, and with items like Sunfire Cape mixed in with AA's several tanks are quite adept at taking a max life-steal carry on.
Tanks have Thornmial, which is way better vs. lifesteal that Grievous Wounds ever was.