DERG
The torque discussion is interesting. I read somewhere that the Trent 900 engine series accelerates from ground idle to maximum TO rpm in something like 5.3 seconds. Seems like a lot of twisting/torque going on in a hurry.
All rotors are balanced after blades are inserted into the disc prior to actual assembly into the module build. Each blade has been weighed to the gram and may be inserted into the disc based on weight distributions. The balancing machine is like that experienced in an auto tire shop except it is more sophisticated and goes to higher speeds.
After final assembly of a new engine, it is filled with oil and put on a test stand to run through its paces while being closely monitored. Vibs are examined quite closely as well as EGT margin. The process takes about 3 hours of engine running time to complete. If all is good, the engine has the oil removed and it is packed up for shipment. If it is not good, the engine is returned to dis-assembly to figure out what the problem/problems are. This doesn't happen often but when it does, the engine is known as a "hanger queen".