ToME: the Tales of Maj'Eyal

I just started an archer, wanting to specialise in "slings."
I accidentally clicked and realised that you have the ability to wield something in your offhand along with your sling.
However, as I am DEX based, offhand attacks are of no importance, nor do they trigger with the "shoot" function.
How does the sling work in conjunction with the offhand stats such as armour penetration, crit chance?
Does it not do anything as the armour penetration/crit chance et al only count for the offhand weapons attack?
Thanks .

You could wear a shield. You can also carry around an offhand weapon (a dagger or mindstar) that gives bonuses "when wielded or worn."

Doh! That totally crossed my mind.
On another note:
Is there a way to know which classes can "dual wield?"
And thanks

All classes can dualwield, but it is restricted to daggers and mindstars for all but one. Dualwielding is good on many classes though, basically any non-mage that does not have item dependent skills like Shield Wall or the Berserker talents.

What happens with "quick" weapons when dual-wielded? Do you attack at the speed of the slowest weapon?

Thanks for the answers everyone.
@wobbly,

You have two weapons. One has an attack speed of A = 100%, the other has an attack speed of B = 80%. Assuming these weapons act alone, what is the most appropriate "overall" or "average" attack speed?

In 8 turns, weapon 1 hits 8/A = 8 times.
In 8 turns, weapon 2 hits 8/B = 10 times.

Or, if hits were dealt on the same action, you could instead attack (8 + 10)/2 = 9 times, hitting once with each weapon. This is equivalent to 8/9 = 88.9% attack speed. Generalizing to any attacks speed A and B over X turns, we get

X/[(X/A + X/B)/2]=2/(1/A + 1/B) attack speed

which is the harmonic average.

Dont quote me on that though, I just started this game. xD

Yeah, I'm pretty sure you attack at the speed of the slowest one.

Also, it's good to keep in mind that you can't melee with a sling. If you have a sling and shield, you punch enemies; if you have a sling and dagger you attack with only your dagger.