it's not a bug. It's to make Donatra more unpredictable and challenging. The pulse sometimes stray outside the green lines, as well. We'll have to come up with new strategies. I like the changes, because she was boringly predictable.
Apparently it is intended for her to cloak more, regardless of how close you get to her, for her to move at unrealistic speeds and maneuver better than any ship in the game while cloaked (I just had an amusing run where she decided to cloak, then within a few seconds appear 40km away for some reason), as well as be immune to any ability she wants. You tractor her, she cloaks and runs away. You use graviton pulse or any crowd control ability for that matter, she cloaks and runs away. She moves through warp plasma and theta vent without breaking cloak. She decloaks and fires her instakill weapon at any time she wants regardless of the animation, then fires it again, then she cloaks and runs away.
I liked it harder for the first few days until I just had a pug last 45 minutes. One person gave up 6 minutes into fighting her, and the rest of us were stuck putting up with her for the rest of the time. I've run it a good 20 times since the changes were made an hadn't seen anything near like this yet. Since she was cloaking no matter how far away we stayed, in the end we only finally beat her by moving in until we were touching her and firing for the 10-15 seconds she remained uncloaked.