I always thought that any IAS affects whirlwind, but I'm seeing on some sites that only that weapon's attack speed is calculated into whirlwind. Is this true? Why do people go for Highlord's on whirlwind barbs?
Also read that life tap from Dracul's doesn't trigger from whirlwind. Is this the case?

Is frenzy just better? I saw many people saying that frenzy and whirlwind are about equal.. but I don't want to be building my barb in ways that don't make sense.

Fyi, current barb I'm using is single player hardcore using:
Doombringer (shael)
Lightsabre
Vamp Gaze
Lionheart boneweave
Mahim-Oak (but I just found highlord's and was gonna equip, but I'm not sure anymore)
Ravenfrost
Rare life steal ring
IK Boots
IK Belt
IK Gloves

I have some other good items I'll equip soon but haven't yet cuz of resists (Gore Riders, Verdungo's..)
Can someone advise about gear I should be using for whirlwind build. It never occurred to me that some of these mods were useless with whirlwind, so now I want to better understand what to get and why to get it.

Any other tips about whirlwind barbs you think would be useful for me to know are appreciated.

About LT from dracs, ctc = chance to cast does not work with ww.
And yes, only wpn ias counts on ww, just like on a shape shifter.
They use Highlords for the Deadly strike.

whirlwind is so dangerours
i would ever go frenzy or berserk with a decent equipment

Hlords is one of those most damaging items in the game. Guillaumes, Laying of Hands, Hlords, Grief, Razors for java etc. There is whole tier of extremely overpowered items.