Raspberry pi performance should not be the issue, since Bitfury made miners with hundreds of gigahashes using raspberry controller. Software can be causing low performance though.
Titans put a hell of a lot more stress on the CPU than old Bitfury rigs. BBB's are the way to go for more powerful miners.
Also be sure to have a good SD card. My Bitfury rigs had constant corruption problems with the crappy SD cards that Bitfury supplied. Once I replaced them with high quality cards, my problems went away.