Because I was looking for myself and can’t find anything:
Stats can be found at this excellent and useful location, updated regularly: New! All Updated Hero Rosters (including costumed heroes, trainer heroes and family bonuses)
Just FTR, I’m over two years in (25 months next week), and am still missing Quintus, Justice, Kadilen and Lianna, finally having received Sartana from TC20 yesterday. I’ve had one TC20 running for about a year and a half, and a second started a few months later (both almost continuous, with just a couple of weeks off).
More stats: There are 20, four of each colour, 8 fast, 8 slow and 4 average.