Gday Will, I was also under the impression that the Rover PAS pumps were not all that powerful for driving winches.... unless you changed it over to another type of pump I guess. I run an old school Warn XD9000 which has been pretty good and have had no dramas with the electric winches running off the standard battery. With an auto you should be ok, though stalling manuals has been a prob in the past. WRT heat buildup in the drum, I'm pretty sure this is due to a brake in them and should be ok for pulls. Actually you can now get plasma type winch cables for low mount electric winches.
In terms of power, the Warns are 4.6hp I think, and stepping up to about 6hp or something similar, though I wouldn't get too hung up on line speed, for our use its more about pulling power.