I'm 3.5 hours in, qualifiers are crap so far but got pretty good non-qualifiers. 37 ED RJoF, decent skillers, couple of nice SCs:
For me after 3.5 hours Trapper is at 194 cow kills/minute based on rune drop count, but I don't trust that number yet either. According to drop count she started with 258 kills/minute after 20 runs or so

because during the first hour in general runes dropped left and right, then last hour very few runes dropped at all, long stretches where I got runes not even every other run. Let's see how things look after 20 hours.
Thanks for sharing your data
@Gripphon, good to have some comparison (in particular my rollercoster in rune drops had me wondering what was actual average of rune drops per run, but my numbers aren't very different in the end).
It took me about 1.5 hours to I realize that FB dmg even with Beast setup is enough to put P5 cows in hit recovery – that's pretty a important thing and triggered a change in gameplay. Now teleporting directly onto the edge of the cow group on Beast switch to max Merc dmg, staying next to Merc while laying down DS and throwing FB just next to her on Merc basically. As long as cows don't encircle her, they just stand there looking stupid and inactively awaiting death. Overall runs became smoother despite 1 frame slower teleporting with Beast switch. Only issue with this playstyle is when I'm Amp'ed – then I sometimes have to take a step away or use Mind Blast to keep her and the Merc safe until the curse wears off.
Run times currently at +/- 2m20s on P5, picking up jewels, amethysts, Rals, rare rings and charms... so could be a little faster when only going for qualifiers. Recording of new playstyle to follow when I don't run the risk of embarassing myself by dying.

Still getting the hang of what she can and what she cannot face tank, had two deaths and two S&Es following the change in approach...