The matter is all about controlling the whole process; an .icc profile, as you know, is a passive command on colours. Though I use .icc profile for colors (I use an old version of EFI with ECI RGB charts and a Pulse), for BW prints with K3 inks I absolutely prefer QTR. It is a real RIP on the fly and it leaves total control over inking.
I figure you know what I mean: different papers behave differently under certain lighting conditions, and the Toner control lets you balance the warm/cold tone respecting crossing tonal values. This is a great advantage.
QTR does not fix a white point, an .ICC profile has a fixed white point.
Toning inks (LM/LC) let you decide whether for cold, whether for warm prints. Adding a bit of yellow or cutting black tones and Bòack boost introduces sepia toning. And this you can do directly. I sometimes make use of Epson ABW, for which I have a whole process using Duotone curves (.ATF file I add to final image before printing), but QTR behaves better, I think.
So, finally, my trouble is relating the Gray Curve and the Linearized L values with a simple curve in Photoshop, a curve that I can upload to the single Toner mask to balance the warmth or coldness of L line.
Hear you soon,
Lorenzo