We already saw that the Threadripper 2990 is starved for bandwidth between Zen packages due to the infinity fabric design. So you get incredible cinebench performance (and some other 'embarrassingly parallel' workloads), but it doesn't scale to other kinds of programs that have more interthread/interprocess communication. I guess it remains to be seen what happens with EPYC, but my initial guess is that it will have…
Yes, infinity fabric has limitations.
Threadripper suffers in memory intensive workloads because only half of the CCXs have a dedicated memory controller thus some cores need to talk to another CCX to access memory.
On EPYC each CCX has its own memory controller so it's less of an issue.