Is it ok to send a descriptive intro letter alongside a pitch deck to a VC?
No, don’t do that.
Instead, and importantly, really nail a “one paragraph plus a few bullet points” email. Hit the high points, get the extended elevator pitch (with key metrics and progress points) just right.
Write an email that stands on its own. That a VC would fund even without a deck. An email that is that good. And not too long.
Then attach the deck anyway.