Even when Resolve was only ever those two modules (and back then the edit was pretty basic) I thought it was incredibly good. DaVinci's dedication to publishing free (of charge) software is one of the few things keeping Adobe in check.
psst, rumors say that Grant Petty wrote the original drivers for AJA. wikipedia doesn't even seem to have an entry for AJA the company.
When I used Resolve several years ago the system requirements were high but you could mitigate that by using a proxy workflow.
"DVI-to-DVI Connection
Connect one end of the DVI cable to the DVI connector on the SDI Output card and the other end to the "north" DVI connector on the NVIDIA Quadro FX 4600/5600 card as shown. The SDI output will not work if the cable is not connected to these two connectors."
So it was an external pass thru type system that just converted DVI to SDI. They joined the daughter card via external oddball cable rather than making an internal ribbon cable connection.
Not much need for them, either. As long as you have an HDMI output (or a DVI output with a passive HDMI adapter cable), there are HDMI-to-SDI converters. Blackmagic sells 'em for like 70€ apiece - I've disassembled one, it's essentially a HDMI decoder, an FPGA that does the protocol translation and an SDI encoder/transceiver.