I do firmly believe that N BBoY>H KTT for us, and ill explain why. Your comment about the combustion nerf certainly is one facet, but at the same time because combustion is so much lower of a proportion of our damage than it once, it makes sense to not make our trinket choices specifically because of combustion.
With pyro being so much of our damage output, the haste on BBoY helps immensely, not only does it help with output in and of itself, it'll also boost your 2p uptime=more FB/pyro. The other factor I would like to touch on is that we dont need combustion to utilize a stacking int pro beautifully. As you said, if played right we have chain pyros at our disposal at command. Assuming all crits, you should be able to triple pyro when dropping down from the HS+HU combo. So pretty much in my opinion, we can ALWAYS put 3 pyro and an LB on the back end of BBoY. With KTT however, we dont have anytime in specific to time burst to, and a lot of that int proc probably gets wasted by fireballs. Our utility in terms of on-demand burst shines even more when we throw in PoM and AT: 4 pyro in a row, and for AT, save the last 6 seconds of BBoY. yum