From my experience most DTrace users rely on DTrace "providers" [1] and Static Trace Points [2] rather than directly probing kernel structs. Also these days the Solaris kernel is not moving all that much.

[1] https://www.illumos.org/books/dtrace/chp-syscall.html#chp-sy... [2] https://www.illumos.org/books/dtrace/chp-sdt.html#chp-sdt