Are you using the Aqara WSDCGQ11LM model? Are you using Zigbee2MQTT? Did you have to adjust any settings (if it’s even possible with this sensor)?
I am really struggling to understand how mine are reacting so slowly. Within 1 or 2 minutes would be fine.
Yes, Yes, No
Firmware build date
20191205
Firmware version
3000-0001
Manufacturer
Xiaomi
Model
WSDCGQ11LM
From my personal experience: positioning is everything. Experiment with different positions for the humidity sensor. Too much or too little airflow where it resides makes a huge difference.
I don’t think so. My experience with ZigBee sensor, I had the feeling they (force throttle) to conserve battery. Maybe they don’t even take measurements for a period of time so obviously they lack/loose measurements which ultimately leads to low response times.
I ditched all my ZigBee humidity sensor for cheaper Xiaomi BLE ones with display which (contrary to the ZigBee ones) react fast and can even be customized (default broadcasts every 2.5 seconds I think).
The BLE hygrometers are located on the exact same spot like the formerly owned ZigBee ones but react almost instantly!
There is some combination of measurement delta vs frequency. I went back and looked at the past several days, during rapid changes after starting the shower, I’ll see readings every 15-60 seconds. I don’t see small delta’s that frequently, ie a 1% change probably wouldn’t update in under a minute, but a 10% change would. There is gray area in between, I’ve never tried to figure out the exact algorithm, but so far they fit my needs.
I am pretty sure it’s nothing to do with positioning. I’ve been trying to upload the history graph, but for some reason it keeps giving an error. There is no reaction for about 11 minutes and then it jumps by a good few percent, so it’s like the reporting rate is being throttled to once every 5 minutes or something.
Also using Aqara Temp/Humidity sensors in all areas of my house, bought at different times over the past 2-3 years. I also have some original Xiaomi Mia ones as well. The bathroom ones react fast enough, maybe a take a minute or so. I am using a Conbee II and ZHA.
If I just look at a graph it only shows change every 5 minutes but off I tune the reporting down to a smaller period when I know the shower was on, I can see a faster rate of change.
My understanding was that the sensors report on a fixed time interval unless there is a significant change and then report immediately. Not sure what a significant change is, but it seems good enough for my use.
According to Aqara’s FAQ:
If the temperature, humidity and atmospheric pressure vary only a bit, data will be reported once an hour.
If the temperature variation exceeds 0.5℃ (1℉), the humidity variation exceeds 6% and the atmospheric pressure is no less than 25hPa, data will be reported instantly.
From what I have read, this is not changeable in Zigbee2MQTT reporting (seems to be hardcoded into the sensors) and it does seem to correlate roughly with what I am seeing. It appears to be only updating when the temperature has increased by 0.5, which seems to be detected quicker than the humidity increase, which is then getting triggered by a +6% increase. This is probably fine for most use cases, but not for switching an extractor fan on when showering, at least not for how it’s performing for me anyway. Still not sure how others are seeing faster responses, unless some batches of sensors have different reporting limits set.
It looks like the Sonoff SNZB-02 does support configuring the reporting interval, so I think I am going to order one and give it a go. Short of that, it might be a case of setting up some Bluetooth Proxies and going the Bluetooth sensor route as suggested by @indeeed.
@mattdm I would be very interested to know how you got on with the Sonoff.
Those parameters still don’t tell the whole story. I routinely get changes of less than 6% in something closer to real time. Maybe not instantly, but certainly not hourly.
Strange we are seeing such a discrepency in reporting/response with apparently the same sensors. I checked and my firmware matches yours. 
I tried another Aqara sensor (in case the one I was using was faulty) and it’s behaving exactly the same. I’ve ordered a Sonoff and will report back on whether there is any improvement with it.
Report back.
I never liked any Sonoff battery device I tried. Have a drawer full of them, but not temp/humidity sensors.
That doesn’t bode well. 
It’s coming from Amazon, so at least I can return it if it’s no better. I’ll definitely post an update here with my findings.
I have two - one SNZB-02 and one SNZB-02P - for this exact same application (monitoring showing event)
They are quick enough in my setup to trigger exhaust fans, soon after any shower starts.
Wait - I think I reported already. See my previous post from last year (Feb 2022) - with graph.
Back then, I have only got it for a few days. But now, after 1yr and 9 mo, I can say I am still using the same battery.
Yeah, same here.