I wouldn't play two rucks. Rucks are the least important position on the ground and most premiership teams haven't needed a particularly good one (or two)
This is an interesting view that I think has a lot of merit.
I don't quite agree to the extent that I think a good ruckman is a valuable point of difference, and the best ones are definitely worth having
There not enough genuinely good ones, probably 2 or 3, and if you don't have one you are probably better off conceding the position and not worrying too much about who you put out.