Is Riposte broken for warriors?
 

I just trained it for my level 25 warrior, but it doesn't seem to be leveling any. I've been getting hit quite a few times by XP-yielding mobs, so I'm really not sure what's going on, here.

Higher Dex increases your chance of melee skill ups. When you first get a melee skill it is harder to level, because it is lower skill and not triggering as much. Once it gets a few ranks it will level fast.

put some more pts into if you are that impatient, otherwise chill

Isn't riposte a defensive skill, therefore dependent on agility?

I would have to agree on this.