AFAIK Hezbollah uses *mainly* BM-21 rockets designed in sixties.
http://en.wikipedia.org/wiki/BM-21 To get results expected by designers Hezbollah would have to fire all 200 BM-21 rockets into *ONE* target in less than a minute.
http://www.globalsecurity.org/military/world/russia/bm-
21.htm <quote> Because of its high volume of fire and large area coverage, the BM-21 is well suited for use against troops in the open, for use in artillery preparations [...]. One volley from a BM-21 battalion is 720 rounds. Because these weapons have a large circular area probable (CEP), *they are not suited for attacks against point targets*. </quote>
BM-21 was not designed for precision of *single rocket*. It was designed for launching high volume of rockets in short time.