Avi Issacharoff is reporting in a Times of Israel article entitled "A third of Hezbollah’s fighters said killed or injured in Syria" that Hezbollah is suffering massive losses in its battles with ISIS and Syrian rebel groups:
"The Lebanese Shiite militia Hezbollah has seen between 1,300 and 1,500 of its fighters killed in battles in the Syrian civil war, which means that together with the wounded it has lost as much as a third of its fighting force, according to Israeli estimates.
Some 5,000 of the organization’s members have been injured in fighting alongside regime troops against rebel groups, including the Islamic State.
. . . .
In July, Israel Radio reported that Hezbollah had arrested 175 of its own fighters after they refused to take part in battles in the Syrian city of Zabadani, close to the border with Lebanon."
Bottom line: At this rate, Hezbollah will not be capable of engaging the IDF for years to come.