Personally, I can't even imagine doing that. If the opponent has an army of 2-3 stacks, then it might still work. But if they have around 6-7 stacks, they will reach your large army sooner, and without diplomacy and with good morale, they will tear you to shreds. Moreover, what do you do if the opponent is undead or a powerful warlock? And in Heroes 2 and 3.5, there is no intimidation at all. There is only hypnosis, but it can only be used to chase away flies.
A dubious tactic. And take diplomacy just for this? No, thank you.