In my experience, Falkon’s rendering in Genode is quite fast, to such an extent that I’d rather use that instead of the Debian/FireFox combination in some cases (.e.g. TG feeds).
Could it be that you’ve run into this again ? Uncaught 'Genode::Ipc_error' - #15 by hamed The fix provided by @cproc was to add a qputenv("QT_QUICK_BACKEND", "software"); call.
If you’ve run into a different problem and Falkon somehow renders slowly on recent hardware, I’d say it’s worth filing a ticket or investigating, yes
I can’t locate it right now, but there was a set of changes to Sculpt OS a few weeks back, where Norman tweaked the priority settings for nitpicker, leitzentrale, et al. Not sure it’s relevant to your issue though. In my experience the clean separation of components in Genode does not impede performance in a significant way for common use cases (with the possible exception of the fs stack, which Norman explained might well get optimized in the coming year or two). So if that’s not the case for you it’s worth digging I think.
EDIT: on second reading, it seems your troubles are not related to Falkon at all ? As before, you’re gonna have to be more specific 
One thing you could do is leave nano3d running in the background, together with whatever application you’re experiencing sluggishness with… If nano3d keeps running without skipping a beat, you’ll know the problem is specific to the problematic application, and not to Genode and nitpicker…