wearing a shield adds a little to stealth hinderance, so removing it and going with parry could be a choice for someone looking to enhance their stealth. That's the only one that I can think of though.

< You throw a massive lumium shard at a beisswurm. A beisswurm attempts to evade. The shard lands a harmless blow to the beisswurm's abdomen.

Parry trains a little bit of weapons and learns at a secondary rate for many guilds that are armor tert.

Parry has the smallest multi opponent penalty and receives a bonus if you parry with a weapon with which you have skill. Once you have significant (read: 300+) ranks in the weapon you're parrying with, it will be a superior (IMO) defense when you're engaged with the maximum number of melee critters. This highly specific answer is the only real use for it right now, I think. Hopefully that changes in combat 3.0.

Basically, worth having since learning it is pretty painless (just switch stances for a couple minutes), but currently don't expect it to be like shield.
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Malkien