Well, remember that the JT8D was a turbofan conversion of the turbojet J52 (see A-4 Skyhawk & A-6 Intruder), so there was little left of the original subsonic engine... and converting the JT8D to the RM8 involved more than just "sticking an afterburner on" - the Swedes had plenty of experience by then in modifying jet engines.
Note the comment in the Wiki article:
RM8A -
AJ 37 Viggen
Since the original engine was constructed for subsonic speeds, most parts of the engine had to be redimensioned for the higher Mach-speeds in a military aircraft. Fans and turbine were altered, a new burn-chamber designed and a totally new fuel-control system for both engine and afterburner.
The TF30 was a clean-sheet design (but strongly based on the JT8D, ironically) specifically for SUBSONIC aircraft (FD6-1 Missileer and the VAL A-4 replacement program, won by the A-7). So the entire design had been created without thought of supersonic flight - the first stage really needs to be designed differently, and it takes more than intake design to allow a sub-sonic engine design to deal with supersonic flight.
That the A-7A/B/Cs had no issues with compressor stalls etc, while both the F-111 AND the F-14 with its completely different intake design did experience them regularly, indicates that there was something about the basic design that was not compatible with supersonic flight - and which Pratt's engineers either could not, or
were not authorized by USAF/USN to spend the money to, correct on the production engines.
The TF30 in the A-7 had had an issue with steam ingestion during catapult launches, but this was easily corrected by modifying the 12th compressor stage.