There has been some talk before about the fact that Khalida is an underperforming and also overshadowed Legendary Lord option for the Tomb Kings. Besides that, some of us also believe Khalida suffers from untapped potential in her niche/role. Based on the community discussions held in the recent past, I would like to propose the following to improve her:
1. Increase her armour value on the Necroserpent mount from 90 to 110. There is no reason (other than an oversight) why she did not get the same buff as the other Necropolis Knight units.
2. Give Khalida a munition-based, short to medium ranged attack imbued with poison (80 or 140 range), since her staff spews venom in the lore. This way she can complement her abilities and support the ranged Tomb King builds much more effectively and consistently. It would ultimately make her more unique and more desirable a pick as well. Her price can be adjusted accordingly, of course.
I sincerely hope you will consider these proposals. Khalida is really in need of some help.