Weapons
As you know that long range weapons work better than short range weapons, because they cover a wider WW path hitting more targets and compensate for sloppier whirls. Additionally, long range weapons can hit (and possibly kill) your targets before they are in attacking range. Within the same weapon type/range, the most desirable attribute is of course the damage it does, everything else such as life/mana leech and +skills are just icing on the cake. When choosing between weapons with similar stats, let me suggest some often overlooked attributes either from the weapon itself or other items - attributes that will make you WW more efficient and/or fun:

Bear - Knockback target
It's a compromise with a large mob. When you push them back out of range they cannot hit you, likewise, you might not be able to hit them during the same whirl if they are knocked away from your reach. However, the tradeoff is in your favor when you have low HP, defense, or you are in over your head. With small mob and singled out boss it works great when you position yourself to knock them back inline of your WW path. Targets being knocked back suffer the same fate as being stunned in that they are unable to attack you until they recover. When knocked back inline you will continuously hit the targets until the end of you WW, in essences making multiple passes with the efficiency and cost of one whirly.

Blinds Target - Similar to the Necro's skill Dim Vision
Similar effect as wearing an Ice Blink or other cold damage adders; when hit, they stand in place dumbfounded just like they are chilled - but leaving corpses intact for your Necro partner and Find Item :)

Vileness - Prevent monster heal
This is more useful for the under powered or those soloing in a large game when you need many WW passes to kill, and for those who lacks focus to finish off what they started(hurt) first. Unlike poison damage, prevent monster heal from Vileness has no duration so once a monster is affected it will not regenerate life.

Howling - Hit cause target to flee
When you have low HP, defense, or you are in over your head. It can work the same way as knockback with small group. Fleeing monsters still within your attack range are defenseless. Try to get them to flee in your WW path or have them blocked by other monsters or structural features. However, this is easier said than done - monsters flee at "run" speed, faster than their normal walking speed.

Left Mouse Button (LMB) VS Right Mouse Button (RMB)
Why LMB? Saving the RMB for skills not available for the LMB
Typically, the left clicker chooses a target within the mob and executes WW. This is not very effective since the WW cycle stops short right at the target and only hit the target once instead of going through the multi attack cycle; what's worse, the target you click on is probably not the last target inline due to stacked sprites (this happens more when the monster sprites are larger). The maneuver is the same as throwing yourself at the enemies and let them get free hits on you. Of course the left clickers can always use Shifted-Click to go pass the last monster inline but that would just be a less efficient right click ;p

Problems with LMB:
- You need to target.
- You need a target. Someone might kill it first then you end up walking and get hit in the process
- Putting yourself at risk more often.
- Lost of accuracy. With a mob especially with large monsters, selfdom can you target a specific monster. this might shorten your range of WW travel when you click on a target closer than intended.
- Not having 2 attack skills readied at the same time. WW on RMB and LA on LMB, for example.
- Worst yet, you can't use the Dance of Death tactic ;p

Tactics
Fringe or cut thru the pack?
Most times, cutting right through the mob is the more efficient way as long as you have decent AR and the HP (or enough life leech) to compensate more chance of being hit. Fringing, just whirling around the outside parameter of the mob, lets you concentrate on finishing off injured monsters first while keep yourself from more attacks than you would incur by going through the mob. Fringing is also safer when facing Cursed boss packs or cursing AKs. You will have a better chance to escape safely if you are cursed with IM mid Whirlwind.

Dealing with LEB
For singled out LEB - Right click (pass the target) and left click (pass the target) right away to walk pass the LEB. You will still get hit occasionally but the chance of getting hit is lessen by a great degree. Even if you get hit this gives you the chance to drink a potion because you are out of the WW cycle.

"I can still drink a potion when I stop after a WW", you say. Yes, the keyword is stop. You stop and get hit by more bolts and let the LEB close in. LEB being unique monsters, do not regenerate HP so your can take you time to wear them down.

LEB in a mob - Another way is to have the LEB as the first inline with monsters directly behind the LEB in your WW path. so when you hit the LEB and get zapped. you are already hitting another monster to steal life back.

Pre-drinking works with both methods as well as right before you dive into any mob.

The Dance of Death
In Classic Diablo, The Warrior can do a great job tanking for his partners especially when he employs the shift click method and let his partners satellite around him to help pick off the enemies. The WW Barb in D2 is much the same as a TeleKill happy Warrior. You just hope he doesn't over activate, never mind tanking for you. And who can blame the Whirler, any other attacks just don't stack up to Whirlwind's damage and speed

Take a look at the DoD WW pattern and compare it to the normal WW pattern on top of the page and see the difference. What advantages does the DoD offer?

When most people refer WW as a crowd control skill, they are really saying it's a skill that can kill mobs fast. How can a Barb protect his vulnerable partners when he WW halfway across the screen every time. How is that crowd control when more monsters wander off after your partners than ones going after you? Worse, when you WW into new territory you would just activate more monster to add to the chaos.

Can WW be used as a true crowd control skill - actively killing and protecting his partners at the same time? DoD does just that! DoD allows you to use as large a space, or more importantly, as little space as possible to operate.

Crowd Control
The DoD Crowd Control animation shows DoD cutting down a mob with just a couple of inches of real estate (could be less than what is shown, but it's hard to WW while trying to keep a steady rhythm capturing screens). Note again it's a continuous WW with no overshoot.

By using less real estate for your Whirlwind you:
- Activates less monsters
- Mob can easily follow you therefore
- Less scattered mob to kill more efficiently and
- Less strayed monsters to attack your partners
- With you being the tank, your partners can deal with a concentrated mob rather than one that is scattered all over.

Execution
"Okay, okay. Would you just get to it and tell me what this is all about, How do I do it? I am convinced this is the most awesome thing I will ever learn in D2 history. It's even better than TeleKill! But wait, I can envision the lives I will be saving with this tactic, not to mention my own. And there's more, with all the SOJs I'll be saving I'll give you one if you act now!"

It's really ridiculously simple to execute a DoD!
On uniques with lots of life - Initiate a WW with the RMB and keep the button down. Then just wriggling the cursor on the monster will keep you in WW and hitting the monster without any time wasted on overshoots. Just make sure the initial right click is not on a target, otherwise, you DoD will end when that monster dies

The Last Dance
What is even better than fringing Diablo with WW? You guessed it - the Dance of Death.
When tanking for weaker characters with low HP and or low resists the best thing for a barb to do is use a stationary attack such as Bash or Leap Attack. Do yourself and your partners a favor, cast Battle Orders to give everyone a boost in HP and Mana and refresh it before it wears off. The use of stationary skill is to stay on one side of Diablo taking all the heat while your partners stand anywhere but behind you avoiding the LBOD altogether.

What if your partners are not so weak that they can't take an occasional single lightning bolt. What if you are weak, not being able to take on too much LBOD yourself? What if you are soloing? Go ahead and dance the Dance of Death, You will kill faster and get hurt less. The DoD goes many steps better than fringing Diablo with normal WW as discussed earlier. With a little practice, you too can perfect these fancy steps shown in the Izzy (the first DoD) animation. When you can hug Diablo while you are whirling around him you achieve two things.
1) Retaining the tanking position in coop.
2) You will seldom get hurt by the LBOD. When you do get hit, you'll only take a fraction of the damage from a single bolt (not the entire breath) because you'll be out of range before the spell duration ends.