So, I've found this link which seems to give a more detailed breakdown of how many questions there are per topic than the mere "50% calculus/25% algebra/25% misc" outline: https://gremathsubjecttest.weebly.com/t ... erial.html
It seems like this was based on data collected around 2010-2011, so things may have changed. For those who have taken the test more recently, does this seem to be accurate? In particular, are there actually few enough questions about multi that it's a good idea to focus more on getting faster at single-variable calc + linear algebra instead?
A lot of what this page says is correct, especially with regards to "compute first, think later". However, I think the page very much underestimates the "Other materials" section. On GR1768, I counted 6 problems having to do with groups and rings alone, and there were plenty of real analysis / topology questions to match. Also, complex analysis is more than just residues (it's worth noting that both GR1768 and GR0568 do not have a single complex integral) --- you also need to understand basic functions of complex variables and the Cauchy-Riemann equations, among potentially other topics.
It's also important to understand that the proportions tend to vary from test to test. I've taken tests where there wasn't a single topology question (as far as I could tell at the time, at least!), and I've taken others where there were two or three. So, trying too hard to guess how many questions of what type there will be may not be productive. Take what you see with a grain of salt. That being said, you're absolutely right that facility with calculus and linear algebra will be essential to doing well on the test, so yes it's essential to have those down.