Hello,
not sure if any of the maintainers has seen https://www.curseforge.com/wow/addons/pitbull-unit-frames-4-0?comment=7143 - but I had the same issues (doing a world boss, frame rate drops to 10, or even complete freeze for a second) every 5-10s, very much unplayable.

Today Blizzard have seemed to have done a patch again, so I'm trying to switch back to PB4 today (I've been using Zperl for a week because of this) and try to repro, but BugSack was empty all the time but I did get one of those "do you want to disable PB" popups when going to edit mode.

I love pitbull. It's the best looking and best configurable unitframe addon there is. Sadly I also had to switch because of fps issues.

I used the addon "Addon Usage" to see if I could find the bottleneck. It seems like pitbull updates a lot on every single frame and thus taxing the CPU. E.g. updating the text of the level of any given character. An information that for sure wont change 120 times a second :). This gonna hog your fps. Especially if you use it to show 30 raid frames. This gonna be a challenge to turn pitbull away from tick based updating. A challenge I'm not up to :(

I switched to shadowed unit frames, which comes pretty close to the feel of pitbull. Shadowed unit frames is from the ground up written that everything updates based on events and not on every tick. Which makes the addon incredibly efficient. If someone would refactor pitbull, I'd switch back in a heartbeat though.

e.g. this is the average cpu usage of suf after a bossfight in a 5 grp, just 2.5ms per second cpu usage.

pitbull would have topped that chart with some frame drops :/

I tried pb4 again in classic, but it causes horrific performance in 25m raids. At this point I'll need to port all my extensions to new addon, probably shadowed UF as this doesn't seem to really be an easily fixed problem (nor do the maintainers seem that active)