Recently heard talk of such a macro, that if it were disclosed, it would get nerfed. I reviewed the footage, and it 100% show’s that the warrior keep’s Shield Wall active while he swaps to a 2h weapon. I logged onto the PTR to test this and I couldn’t get it to work…so this is 100% an abusable bug that some high level pvp’ers are using. They don’t want to share the macro in fear of it getting nerfed either, so that goes to tell you something is fishy.
Edit: Reviewed more information - you only need to equip the shield to activate Shield Wall, then you can re-equip your 2h wep and you won’t lose Shield Wall. This is 100% a bug that needs to be fixed as you should lose the buff when you don’t have a shield on.
Edit 2: Shield Wall bug on PTR
Hmm… this is interesting. How should the buff behave? The buff just says that it reduces damage taken. It does require a shield to be equipped on use… but doesn’t explicitly state that you need to keep it equipped for the buff, nor that you should lose the buff if you swap weapons.
If indeed this is a bug, and not working as intended, I would imagine the buff could be changed to only apply while a shield is equipped, but still allow the warrior to weapon swap during it without losing it.
Have you confirmed that the buff does indeed apply when a shield is not equipped? (not just by seeing the buff, but by checking your combat log while being hit?)
EDIT: I tested it out on some mobs in the world, and it seems to apply even without having a shield equipped.
Shield Wall Requires a Shield
So Shield Wall should behave as follows:
Does the warrior have a shield on? Yes. Shield Wall buff can be activated.
Shield Wall is still activated but warrior swaps to a 2h weapon. Shield Wall deactivated due to not meeting the requirement for the buff of needing a shield.
100% a bug that should be fixed.
idk, that seems really punishing for a 15 second buff on a 4 minute CD. It could either work as it works now, or only apply the buff while a shield is equipped, imo. But having it completely drop when you weapon swap (when warriors swap weapons a lot) seems overkill.
Just my 2 cents 
The thing is, they need the shield equipped. So you shouldn’t be weapon swapping from a 1h wep+shield after you hit shield wall to a 2h wep to continue to pressure your opponents. 100% not working as intended.
To activate the buff, yes. The buff itself doesn’t say anything about requiring a shield to be active.
If this is indeed the case, then hopefully this bug report gets noticed
In any case, as noted:
The buff IS removed if you have the following: 1h wep+shield and you swap to a 2h wep.
The buff ISN’T removed if you have the following: 0 weapon+shield and you swap to a 2h wep.
I tested removing the 1h wep after I popped Shield Wall and then put it back on then removed the shield and you can see what happens to the buff…
I immediately lost Shield Wall when I removed the shield. It could be some spaghetti coding to do with having a weapon in the Main Hand, but that’s all I’m seeing…I do hope this get’s noticed.
Bonus: You can stance swap too…
Oh, is that right? I’ll test it out.
I tested it swapping from 1h + shield to 2x 1handers. The buff is not removed in that case.
Interesting!
EDIT:
Yeah, I found that swapping to a two-hander drops the buff. And that when swapping from a shield and no mainhand to a 2hander, it doesn’t drop the buff. This would lead me to agree with you that it’s a bug and should be removed anytime the shield is unequipped. Either that or dropping the buff on any weapon swap is a bug, but I think this makes less sense than it only applying with a shield equipped.
I’m curious what happens if you get disarmed with the buff active.