Well that makes it for most 2 hands about 4-5 procs per minute meaning that since it lasts for 15 seconds so 4*15 60 seconds so basicly you are having that +100 strength most of the time.

While it is true that most, if not all, enchants work on a Proc Per Minute basis, Haste increases the proc rate of Pre-TBC enchants, but not post-TBC enchants. Thus the number of procs you get per minute from things like Fiery, Lifestealing, and Crusader all increase while under the effects of haste. Procs like Mongoose and Executioner do not increase under the effects of haste. Refer to this thread at Elitist Jerks for more information:

http://elitistjerks.com/f31/t15553-proc_per_minute_mechanics_haste/