I have in the past but I've lately returned to using a single mono amp block and gotten off of dual L/R amps (too much hassle + cpu to ideally also maintain dual L/R drive blocks). My rotaries come after other stereo fx (delay, chorus and stereo shift / harmoney effects between mono amp and hard panned stereo cab), so configuring 2 rotaries left and right preserves the signal from those previous stereo fx better (mostly delay is the concern as I would not likely run rotary and chorus or pitchfx at the same time). The dual rotaries also adds a bit more interesting rotary goodness along with the dedicated PEQ for rotary.
Edit: Maybe I could go down to 1 rotary block in Ax3 just after the amp and before stereo pitch / harmoney fx and stereo cab - I'll try that to see how I like it, but, for load balancing purposes (all my presets are kitchen sink), I like to offload some functions (rotary / synth) to the Ax2 spdif'd to the end (trading my Ax3-mk1 for an Ax3T would allow me to ditch the Ax2 mostly - but I like that I can have Ax3 + 2 editors open at the same time, as well as having another loop available to use out to an external power amp and back from a load box di out, so the current Ax3+2 config remains).
Edit2: I've heard so may good things about Strymon Lex that I've also been tempted to get one of those and have it in loop2 for rotary, but at $480 Cdn + 50-60$ for their ridiculous proprietary midi cable I don't feel it's worth it with the Fractal Rotary being as good as it is even in Ax2