Keeping in mind that I infrequently use Wing Clip, and that sometimes an Immolation Trap misses and wastes time in combat, I tried to evaluate Counterattack's usefulness by running some tests on Young Stranglethorn Tigers, one at a time in batches of ten, using various combinations of only Raptor Strike, Counterattack, and Mongoose Bite. For the tests I kept my pet dismissed and used no other attacks at any time or buffs other than Aspect of the Monkey in an effort to normalize the results as much as possible.
While Raptor Strike and Mongoose Bite were doing the lion's share of damage, Counterattack generally represented 5% of the overall damage when it was brought into the mix. As I said for Immolation Trap, five percent is not insignificant. My average dps across tests was 47.2.
And yet it's clear that Counterattack is not really designed for melee. It does fair damage, but the attack immobilizes the target for 5 seconds and cannot be blocked, dodged, or parried. Like Wing Clip, the real purpose of Counterattack is plainly to allow the hunter to escape to a point where he can resume ranged attacks.
The trick, then, to maximizing melee damage is to make every attack hit as hard as possible. This means more than just using a hard hitting two-handed weapon. It means maximizing your crit chance and adding in more damage whenever and however possible. Using a good weapon is a start, but I found that using a weapon that has a chance on hit proc is even better.
After looking at my average dps, I applied a bottle of Shadow Oil to my polearm. Shadow Oil gives your melee weapon a 15% chance on hit of casting Shadow Bolt (Rank 3) at your opponent when it hits, causing 48 to 56 shadow damage. My dps jumped from 47.2 up to 53.0, a full 12% increase. I also observed that the chance on hit effect did apply to my "special" attacks, proccing after Raptor Strikes and Counterattack as well as regular melee attacks. I also saw that the Shadow Bolts would occasionally crit. This is great news. Those pitiful Wing Clips, for example, now have a 15% chance of hitting for 61 damage instead of 5.
Granted, Shadow Oil isn't a panacea, because it doesn't scale. But looking at this effect in a generalized context, it points out that a weapon that naturally carries a chance on hit, like the Diabolic Skiver or the Grim Reaper, has the potential to greatly improve your melee results. I've not yet had the chance to test out a DoT effect from a weapon versus a simple bonus attack such as the Shadow Oil provided, but I've procured a Poison-tipped Bone Spear that I intend to begin using.
With my next major melee attack, Kill Command, not coming until level 66, I'll continue to look for ways to improve the immediate efficacy of my physical attacks.