Where are the CITADELS ?

I have a level 94 amazon and 96 invoker. All altas tree max out except for arbiter as i could only find TWO citadels despite after clearing probably 100++ nodes on the map.

Hey GRINDING GEAR GAMES, how many more maps to i have to do to find more citadels ? Is 500 more maps enough ?? Will i be able to find more and clear t4 arbitor before new league ? Is there a special criteria to find those citadels ?

Dear GRINDING GEAR GAMES developers, please kindly advise.