I've been testing whirlwind a lot recently and here are some experiences i'd like to share. When it comes to weapons, Grief Zweihander performs better than Grief phase blades, i didn't think the extra range would matter much but boy was i wrong, it's overall a more effective killer machine with the increased range, notable on packs. So best pvm whirlwind weapons(dual wield) would be from best to worst , Grief Colossus Blade(expensive, needs high ias roll) ---> Grief Zweihander ---> Grief Phase blades ---> Grief Berserker Axe. Technically Grief Berserker axe would be equal to the Colossus Blade in damage output but due to low durability it's imo by far the worst, both Zweihanders and Colossus blades got double the amount of durability compared to Berserker axes meaning they will last a while and the ''indestructible mod'' on phase blades won't be missed too much imo, Berserker Axes were just annoying to play with but each to their own, if you can handle repair every 8-10 min then the damage is top thogeter with Colossus blades. When it comes to armor choice, Enigma seems to be imo the superior choice for everything except ubers, fortitude looks nice on paper but when we factor in the merc and teleport, enigma will crush fortitude using either Reapers Toll and applying decrepify at will(telebombing) with precision or even better, Brand runeword and amplify damage(Have yet to test). Of course, utilizing reapers toll + fortitude is a possibility but isn't very practical imo, merc will not be in position too often and we can't control him and decide where we want to apply the curse, theoretically this combo would rock for pure damage if merc wasn't slacking behind and could be controlled. Best combo for fortitude would be imo a pride stick, going for massive enchanced damage but this did not match the damage of having decrepify at will in my tests, not to mention the defensive advantage of decrepify(higher player settings) or merc survivability with Reapers toll. Finally i'd like to say that when properly geared and built for damage which includes high deadly strike +80%and 50% crushing blow, high strenght(life should not go over 2-2.5k imo) whirlwind has impressed me. In my tests, whirlwind is a notably faster killing machine than frenzy for general pvm, worse for ubers of course. Packs just seem to melt and is the only physical melee spec i've tried(Tested so far: wolf fury, frenzy, zeal) that seems to handle mob packs with a satisfying killing speed. Single Target damage is also powerful using short controlled whirls.