Let's see, casualties in the 2006 war:
Hezbollah: 500 to 600 fighters killed, depending on the source (UN claims 500, IDF claims 600, Lebanese govt estimates vary from 500 to 700)
Israel: 121
So IDF killed between 4 and 6 Hezbollah fighters for every IDF fighter lost. That ratio is worse than in other wars Israel fought, but it hardly supports your claim.
As for the Merkava tanks, they did not have active protection systems installed during the 2006 Lebanon war, which since last year they now do have, so they are no longer vulnerable to the anti-tank weapons Hezbollah was using at that time. Even then, IDF only lost an average of one soldier per tank penetration (out of a crew of seven), which was lower than in previous wars.