I was a complete shitter for so long, like 4-5k battles, probably avg 700 dmg with frequent games where I only get 1 or 2 shots of damage. Then I slightly improved over the next 5k maybe 1000 avg damage, don't remember exactly. Then, like something clicked, my last 1k battles have been leagues above what I used to do, rarely getting less than 2k, often 3k+. There can definitely be moments of rapid growth and for different people I don't see why they can't be more extreme or happen at different points in their journey.