I think Slic3r wasn't used for things like octoprint not because of poor performance, but because the command line Slic3r does not provide any way of getting a progress – there's no way of telling if it hang up, still slicing. Same thing with result: there's no waay to tell if command-line slic3r has succeeded or failed.
Octoprint works with Cura pretty well on raspberry pi 2. It takes time to slice, but that's something. If you've decided to start a print from your phone – you'd be glad you have an onboard slicer, no matter how long (1-5 mins) it takes.
