plain granite
One of the biggest issues is you barely drop heliolite dice and heliolite dice is the one crystal that can pull legendary heroes.
Just put legendary heroes in starlight dice. Since the odds in heliolite dice are 3% for legendaries or at a pity of 35, you could add legendaries to starlight dice at a 1% drop rate and a pity of 50.
lime cedar
I like the idea of having a very low drop rate for a legendary in the starlight dice, but your math does not quite work. With the Heliolite's 3% drop rate, you should get a Lego 1 in every 33.3 pulls. The pity at 35 is to make sure the players don't get screwed by RNG, but they can get lucky and get the legendary champ faster than the expected 33.3.
If the Starlight dice had a 1% drop chance, they would put the pity in the 100-110 range based on the rates of the Heliolite dice.