Its hard to say whether a creature is too hard to correct if we don't know what levels are intended. As a rule of thumb I would expect a creature that is big to be more of a challenge than one that is small. Likewise I would expect an armed or armored creature to be more challenging. I would expect natural armor to be inferior to metal armor.
With this expectation in mind creatures that contradict this logic appear to be out of line. For example, I would expect the Tlokes and Arangmas to be weaker than gobbels, Initiate gladiators, gladiators and Ulbers due to their size and lack of armor and weapons. If they had a deadly string and were extremely agile then it might be a bit more believable.
Some recent observations.. ( not necessarily complaints )
My relevant stats - 50 Sword, 30HA, Armor was plate, some new, some about 1/2 worn out. str,agi,end at 200, q290 sabre, q290 short sword
In most cases I used a bloody stance and fought in place ( no dancing around )
Dark Rogue in laanx dungeon ( first right on the way in ) seemed to be a reasonable challenge.
I got him half way down before I died just fighting toe to toe..
Treppor Warrior in the arena seemed to be unusually strong. Its a little hard to believe that a creature with such an awkward looking body could post such a threat. Fighting toe to toe I had to heal myself half way through before chopping it down.
Initiate Gladiators seem to be too easy. Perhaps its meant to be that way ? These were one shot kills. I do like the fact that there are more weak npcs for less trained players. Also the variety is much better.
Thunder Clacker seemed to be a bit more resistant to attack than one would expect. It was also able to get some hits on me if using bloody stance. with a more defensive stance it did not get though. Was using a pair of 10/50 swords with 1.5 delay. What I'm saying is that I'm surprised that it held up the way it did. Not sure if this is intended or not.