Yes, DSP can add a lot of processing requirements, especially DSD. However, 3.4x is just fine. You need to be dipping under 2x for processing issues to start (I think it is more like 1.3ish actually, but, I’d keep an eye on it if it goes below 2x).
FYI, here is what processing speed means as quoted from the Roon FAQ on DSP (https://kb.roonlabs.com/DSP_Engine)
this reflects the load relative to consuming a full core. “2.0x” means you’re using 50% of one CPU core to play music in this zone.
Conversely, if you were at 50x you would be using 2% of the CPU. So, at 3.4 you are under 50% CPU utilization, ~29.5% CPU used actually.
See my old post for the calculation if interested