The video quality is bad and blurry..microscope and CSI video enhancement requirement.
The rockno is using Stone skin talent, and Revive crest to those wondering about "Best talent choice"
There are 50 Legendary Heroes (up to Cirrina, and excluded 7 for 4 Dragons and 3 Gem Purchase Reward Heroes), 9 Elite, 8 Ordinary and 3 Slime that rollable with gem. Total Heroes rollable by Gems is 70 Heroes. Chance to get 1 specific Hero is 1.43%. So, good luck.
My calculation at my signature, is just mathematically statistic. The best way to understand how IGG Heroes Gem roll is like you roll a 70 face of dice, and hope it will lands on your number. As you know, you can roll 100 times, but your number dont appears at all. And there are time, you roll 10 times, and it will just give your number everytime.