I haven't played Persto, but I did do multiple Netracell runs on the lab tileset. Depending on the room you're in things can get harder or easier, since well, LoS, but I had no trouble hitting things I intended to hit. I was also paying attention to both the minimap and the enemies in front of me to check how many red dots were vanishing after each Tragedy. It wasn't cleaning the whole room, whether because of some surviving Eximus or some walls, but was hitting most of them, and what mattered to me, it was hitting the group i wanted to hit, plus, as I said, enemies I didn't realize were even there in the first place whether hidden behind some obstacles or standing somewhere behind me. I think in the current iteration it only doesn't hit stuff if there's like a literal wall between you and the enemy.
There might still be some bugs as you've mentioned, but I haven't noticed any in my games. To me this new version still lets you hit what you want to hit, the only thing it limits is that you don't reliably hit stuff you don't even know is there - enemies behind walls, in another room etc.
Also i'm not sure how and when does the ability check whether the enemies are in sight. Whether at the beginning of animation, during, or does it "mark" each you see while casting. I had cases when I was jumping down while casting Tragedy and I thought I lost sight of the enemies on the upper floor, but I hit them anyway, so either some bits of them were still seen, or the ability has a particular moment it registers enemies. If it "marks" everyone it sees during the whole animation, then maybe using casting speed actually makes it less reliable since you have less time to "mark" enemies you see? This is just a thing I was wondering about though.