Could you give a concrete example of something that broke in Mojave? I used it a lot in High Sierra, and was preparing to return now under Mojave, would like to know what to keep my eyes open for.
sudo dtrace -ln 'pid50922:::entry {}'
dtrace: invalid probe specifier pid50922:::entry {}: pid provider is not installed on this system
mysql provider's gone:
sudo dtrace -x strsize=1024 -q -n 'mysql:::query-start{printf("%s;\n\n", copyinstr(arg0))}'
dtrace: invalid probe specifier mysql:::query-start{printf("%s;\n\n", copyinstr(arg0))}: probe description mysql*:::query-start does not match any probes
those were really crucial for me. I'm preparing to do a presentation on dynamic tracing next week, and I think I'll have to use a BSD VM instead of using my Mac natively.
It's a bit of a reach to call Instruments a replacement for DTrace. A replacement for a subset of DTrace perhaps. And maybe they'll massively expand it over the next few macOS/Xcode versions. Or maybe it'll suffer the same fate as a lot of Apple's OS features and end up rotting away until it's no longer sensibly usable.
Of course, DTrace works on macOS if you disable the parts of System Integrity Protection that block it (csrutil enable --without dtrace).