Honestly, that jump from 1.5% to 8% is solid. Most people never go back and audit their own sent emails. They just rinse and repeat the same copy and wonder why nothing moves.
The part about stopping the self-referential pitch is huge. Do outbound for a living, and the biggest mindset shift is realising the prospect doesn't give a toss about your company. They care about their own pain. That's it.
One thing I'd add though - even with perfect personalisation, you still have to land in the inbox. Spent hours crafting the perfect email only for it to hit promotions or spam because domain reputation was shot. That's where the technical SEO side of deliverability overlaps with copy. SPF, DKIM, DMARC, warm-up cadences - all that matters long before the first line is read.
For what it's worth, the tool you're building sounds interesting. What personalisation data sources are you pulling from? At my agency we use a mix of firmographic and intent signals. The combo works well, especially when layered with local search behaviour for brick-and-mortar clients.
Also curious what sending volume you're at now with the new structure. Did you change anything else beyond the copy - like send times, subject line length, or list segmentation?
