You can search back thru literally hundreds of posts (from the past 10+ years) of folks having problems with a Firewire audio interface. In almost every case, the user was running a Ricoh, Lucent, Augere, Via, or other "rogue" chipset Firewire controller.
If you want to maximize your odds of success, it makes sense to use a TI chipset Firewire controller.
As for pitting me against Focusrite or any other manufacturer, pfffffffft!
I've turned down job offers from numerous audio software/hardware companies over the past 20+ years.
Focusrite makes some nice hardware... but they're not RME, MOTU, or Lynx when it comes to round-trip latency.