the dash scales on 150% once every 8 minutes,and if he uses it just to get near and do one rocket,then it's a stupid corki too. It's fair because if you build AD,your skills don't deal that much damage unless against a squishy even with those scalings,while if you're building AP/Hybrid (like Trinity Gunblade Magic Pen,changing based on match,not many Corkis do that anymore) your AAs won'tt do much without spamming skills to activate the spellblade. And it's fair because other than his dash he has no way of escape,he has low movement speed so not always he can chase you,if he's CCd he's basically already dead because he has no tankiness and all his skills are not that hard to predict (i don't say easy cause they still have not too much of a reaction time other than his Q that is slow. As you said,little respond time,but not that minimal). He is a ranged carry,the fairness is that he dies as quick as he deals damage.
Just asking,have you tried him in recent times? It's not that easy to deal massive amounts of damage against competent or resistant opponents,since they will eventually learn your way of doing things and start to get better at evading it,or just build for the case (adaptive helm does a good work,if you're a tanky champ who can buy it without problems)