One more thing I'd like to add is that I used the same joint compound in the living room and after about a year and half, I noticed that the texture of the wall where it was applied has gotten bumpy. I assume this is from changes in humidity, but thought this was probably more my fault than anything for applying it too quickly (few thick coats instead of several thin coats) and also, I applied only 1 coat of paint. Even so, this makes me wonder if the joint compound in the bathroom, albeit applied in a much thinner coat, but in a much higher humidity and enclosed space, is destined to fail?

I feel your pain. We used SW Paint in our bathroom and had the same problem; I was so mad because their paint isn't cheap and we used exactly what we were told to use. The bubbling was on the ceiling around the vent but all the walls had water stains from when moisture would drip and those wouldn't clean off at all; it looked horrible. We have an open window and vent that we use religiously, so ventilation was not the culprit.

To fix it, we had to sand down the areas that were bubbling, wash the walls thoroughly with TSP and paint using BM Aura paint. That's what the guy at our local Benjamin Moore store recommended and yup, it was even more expensive then the Sherwin Williams was; it was worth it though because it worked. We followed the guys directions and let the paint cure for a week before using the shower. This did the trick, no more issues. The nice thing is that I didn't want a very glossy finish and the finish of this Aura paint is egg shell. It went on super easy and looks great! Oh and they were able to mix the SW Color I wanted as well which was a bonus!

Next time you do drywall, use a setting compound instead of just a drying mud. Setting compounds like EZ-sand cure by chemical reaction and them getting damp won't turn them to mush like it will mud that hardens by just drying out.

For this issue, scrape, then sand, then sand again. Remove all of the old bubbling paint and any soft stuff. If you have to do drywall repair, use the EZ-sand. For your first time, use the longest open time, which I think is 90. I may be wrong on that, but use the one with the highest number you can find. That's it's dry time. Then prime with two coats of an alkyd primer and then paint with two coats minimum of the paint of your choice. No water based primer. Alkyd.