Sorry, but he is balanced. His damage output is generally always low..... even lower than a Blitzcrank. In other words, most of the time..... he's just punishing you for underestimating his ALLIES.
And it's not hard to get more than 2301 HP damage on him in most fights.... especially in the true damage meta..... and that's at level 18. Low levels much less HP to burn.
He literally cannot stay in a fight. He has to in - out, or he's dead. No other champ has to deal with this paranoia all the time, except Janna and Soraka (champs that serve a different purpose altogether, and don't have enough self damage in their kits).
If you want some suggestions on champs that make his life miserable:

Some are direct counters that make his R unuseable in all situations. (
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Some Heal people out of death or possibly root him for 2-3 seconds.(
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Some are just outright tanks who can taunt/keep up with him. (
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Others have skills you can't escape in time (
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Others outrun him (
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Some have 1 second burst combos which eliminate any chance of getting near them, pulling them, etc (
)
And you're right. if you can't kill him, focus someone else. Or, making him retreat long enough for you to kill someone else. Pyke alone can't defend a base if you wipe out his team.
He's gated by both his damage output and his HP. That's where his balance is. Try Pyking vs a fed
..... her cooldowns are so low that any time you try to escape, as soon as you are "almost" outside of her vision, she Q's you again and R's again. And that's with 45% CDR builds, not 40% ones. I also run Phase rush, so I generally have a MUCH larger gain on escaping than other builds.
I'm not saying Pyke can't exist vs these champions. Many have work-arounds if you are a good player. But.... they generally make Pyke dependent on his team, rather than his team being dependent on HIM. And that's where Pyke loses, and why he's a sub 50% champ.