277 dmg lvl 2

Just wondering if this is working as intended. Played Ornn support vs a Vayne/Ali. Fight broke out at level 2. I was crit for 277 out of 686 hit points or 40% of my hp in one attack. That coming from a hyper carry had me curious if this is intentional balance. I understand it was her 3rd attack doing percent damage but do ADCs really NEED to be doing % health dmg? 40% of my hp after for a single auto attack crit seems absurd for a hyper carry to be doing at level 2. Yes I played badly and am not disputing that and allowed myself to get autoed 3 times in a row. But is 40% of my HP really intended from 1 single attack even if the stars align so to speak? 277 dmg / 686 HP from 1 single attack