Indeed, it’s not much gain.
One idea would be to disable the rules that are based on Symbolic Execution and we know they are more costly. These rules are S1944,S2259,S2583,S2589,S3655,S3900,S3966,S4158.
Another way to gain more insight in which rules are eating up the time is to use the -reportAnalyzer MSBuild option, and then disable the greedy rules for your project…
msbuild /p:reportanalyzer=true /v:d
If you run the build with reportanalyzer, please share the results with us 
In the medium term, we want to gather more metrics on the performance of our rules, any help counts.