On CONCORD not stopping the incursions (and the empire navies too):
The expansion trailer suggests to me that since the build-up ended the target of incursions has been the capsuleers. While CONCORD polices them it is not their role to protect capsuleers from anything but other capsuleers in hi-sec (and that probably to ensure that capsuleers working for the empires aren't overly impeded). The empires made quite the fuss over misuse of assets during the Code Aria inquiry so it is likely that, as with may things that can't be kept private, their hands are tied.
I do find it interesting that CONCORD didn't make more of a showing during the build-up. It is possible that if the Jovians were having issues then, as a member nation whose assets cannot be allowed to fall into Nations hands, CONCORD focused their efforts there.
It's all just complex hand-waving, there's been very little PF on exactly what is and what isn't within CONCORDs sphere and what there is has only served to make things even more complex. It's barely understandable exactly what CONCORD is now. They've been a hall of diplomacy, a police force, a tool of the Jovians, a defender against external threats, peacekeepers, strongly involved in the clusters economy, etc. In PF it has grown beyond it's original roles and become its own entity and it seems either CCP hasn't taken the time to define exactly what this new faction is or they are holding back some surprises from Yulia for later.