2 acres per hour is pretty ambitious. This week I mowed a 3.5 acre plot prepping for i and c peas. It wasn't too badly grown up, it was planted last may. I was mowing most of the time in low range 3rd gear(a pretty good pace, about as fast as I normally mow) and it took close to 3 hours. If I had more time, I'd spray it, wait until it dies and then burn it off, but I want to get it planted before it gets hot and dry.
Without spraying and burning it will probably take at least 3 passes with the disc to get it like I want it. I can usually disc with one pass at about an acre/hr. I have a 43 hp tractor and a fairly heavy 6' 8" disc. The soil is a fairly sandy clay loam right next to a creek. You can do the math and this ain't my first rodeo, I've been doing this for about 30 years