My greatest issue with the D'Shar in my playthrough were the archers and the Scorpion Assassin's/Blademasters.
For the archers: USE YOUR DAMN POLEARMS RIGHT YOU CADS! STOP POKING THE ENEMY AND START SLASHING AT THEM WITH THE SLASHING TIP AFFIXED TO THE POLE! USE IT CORRECTLY YOU PIGSSSS.
From an archery standpoint though, I didn't think they were too bad. Didn't use them too much in sieges however, that's just my experience from field battles. But the moment they step into melee, you've got a tier one peasant. And it is soooo frustrating. Maybe remove their shield for a spell?
For the Scorpion Assassins/Blademasters: "Why did I bother training this guy? It took me 50 in-game days from your last upgrade to get you to this top-tier level, and then you decide to die instantly on me from a tier 3 archer! Come on man..."
"You want me to train some Scorpion Assassins for you my lord? You're giving me.... 150 days...? This is starting to sound like a bad idea...."
*150 days later*
"I managed to train 3 my lord! ... They all died in battle before I could bring them to you.
They die easily. EASILY. For the player, they take ages to train. Then they die in their first battle with their spunky new title. It is very frustrating.
In fact, I think that's my major gripe with D'Shar. They seem to die easily on the field. Sure, they may spontaneously kill a whole bunch, and may be doing very well in battle. But get them into a situation that is a standard counter, like archers being charged by cavalry, infantry taking fire from archers, they drop easy. Hundreds dead.
Their nobles are pretty swell, though, can consequently die pretty easily. (Maybe I'm just too sentimental and can't accept losses. AI certainly can though)
EDIT:
Yes, that was pretty ranty. Holy cow. But from personal experience, it just feels as though no one unit stands out. I don't find myself saying, "Wow these D'Shar archers/infantry/cavalry are great! I can't wait to not replace them with anything else!" It's different from the feeling I get from another unit, like the Empire Armored Crossbowmen. But that's just me. I don't feel as though I can properly convey my feelings about the faction without getting ranty.