The LV profiling relies on instrumentation put in place by the LV compiler and hooks in the LV scheduler, so no, it won't help. I believe the trace tool would show some minimal thread activity, but not routines.
I'll ask on Monday. I would expect Task to be a simplified wrapper over pthreads. I would assume that you can change your own process's thread priorities as lvuser within RLIMIT_RTPRIO values. The LV timed loop and time-critical priorities are after-all run as lvuser.
In case you haven't seen it
http://www.ni.com/white-paper/14626/en/#toc5 and especially the links in section five will give you some background on the linux configuration of the roboRIO. I expect that if you install the operf and other tools that you are set for profiling C++.
Greg McKaskle