Details
NX Plotting in general works to the HP Designjet T2300.
However circles are not round.
It was tested and confirmed this is NOT part file / drawing specific.
Solution
Instead of using the Printer Model of GEN Generic HPGL/2,
use a Printer Model: ++HP:HP DesignJet T1100.
Hardware/Software Configuration
Platform: INTL64
OS: window
OS Version: 1064
Product: NX
Application: GATEWAY
Version: V12.0.1
Function: PLOTTING
Ref: 002-8007214