Abyssal depths Bosses

Hello, do you need to do something specific to get an abyss that leads to a boss? 50+maps so far and i havent seen it once(with the passive points with the 100% increased chance and tablets), not good idea to lock passives progression behind something that random...

I have same issue, 100+ maps - no abyss boss
https://www.pathofexile.com/forum/view-thread/3891702