Torchbearer has occasional, ad-hoc giant monster tours that take it down as an afterthought, and as a result I'd say most of my major characters have the badge. But this one requires a bit more coordination than some of the others, getting started requires some kind of flight power, and it's in an out of the way zone that traditional content probably won't send you to, so it's even less likely to be happened upon than, say, Lusca. Lusca often gets noticed if you are running Manticore, Citadel, or Penny Yin; not this one.
I do think that the rewards should be raised on the GMs that require something more than bumbling onto them and seeing them. like Lusca, Caleb, and the Seed. Right now the most rewarding GM seems to be Adamastor, who does need to be summoned deliberately, but apart from that doesn't need all that much coordination.
I do rather miss taking down three Paladins as a lagniappe when running Manticore and doing the Kings Row mission. Most days there would be three of them, gathered in a specific place alongside the ramp.