Ok we all know that every tier of Fractal level increases agony. This seems the main problem in dealing with high level fractals, but what about the monsters?
Looking at a dredge Fractal (which by the way is the second most hated by me), At level 2 there were 2 monsters guarding the side press platform. While at level 4 they were only 3 or 4 monsters, at level 8 they were about 6. We see they increase in number and this makes it harder, which is fine.
I never played above level 8, but now I'm wondering, if at level 8 we have tripled the monster number compared to level 2, Does the amount of monsters keep growing at this rate or does the monster count remain the same because agony starts kicking in?
Best Answer
The number of enemies does not scale that dramatically. You can read about the differences on the wiki, but the main difference in difficulty is that the enemies become more powerful. This is done by slightly increasing their levels or numbers, adding new attacks at higher difficulties, or buffing certain attributes (such as the movement speed of the veteran grawl in the volcanic fractal).
The increase in number of enemies that you observed seems abnormally high; the increased numbers are usually subtle. That observed difference may be related to those dredge respawning indefinitely. To answer your question: yes they will keep increasing steadily, but not nearly as quickly as you've described.
Note that only bosses inflict agony, so additional agony and increased enemy numbers will rarely be coinciding problems.