Off hand weapon questions

Hi guys!

I have a few questtion regarding off-hand weapon.

Im playing dual wielding stun berserker in delve.

Main hand - mace. Off-hand - sword for whirling blades.

But what exactly does the off hand weapon do?

- I use it to be able to cast blades for mobility

- but what stats shall I look for on it?

- is the off hand weapon just a "stat stick"?

- is it used to calculate global dmg?

- does its fdmg count towards my global dmg?

- do the affises like IAS, LL, etc apply to my / affect my Sunder attac?

It really makes my head spin.

Cheers!

For the most part it does nothing unless it's a Shaper/Elder weapon with the specific affixes "X% of Physical damage added as [Element] damage."

If you don't know what a Shaper or Elder weapon is, just use a two-hander until you find one.

When using sunder, The damage and attack speed is calculated based on the main hand weapon and any applicable skill tree/global mods.
Your main hand weapon should thus simply be a high pDPS weapon

The off hand is not used in the sunder damage so it doesnt need to have lots of locak damage mods like added phys. But it can have global mods like global crit multi, that DO affect sunder. On top of this, if you are using whirling blades with it, the attack speed of whirling blades is dependent on the offhand.
The offhand should have various good global mods, and if you're bent on using whirling blades over leap slam, a good attack speed.

Unique offhand options: Scaeva, Prismatic Eclipse (3 green), Tempestuous steel, the princess...

Rare mods to look for:
attack speed for whirling
global crit multi
damage penetrates x elemental
gain x physical damage as (elemental damage)
certain elder/shaper mods like maim on hit, onslaught on kill etc

thank you guys!

I still have a lot of things to figure out ;)

cheers!

Btw, if this is the case whay u say maybe i shall go 1h + shield for my stun sunder berserker?