Oh also I used all my epic books on Miscreated Monster and Stag Knight, Used two books on jer, but they both went to her A1 and MM still need more books for his A2 cool down. In short, I might not have resources at the moment to make her great.

Speed is super important, and, until you get Arbiter, you really don't have any better people for the team. I'd say Khatun is a very valid choice.

The other two in your roster that are worth considering are Armiger and Fellhound - the latter for campaign farming.

I never bothered with Fellhound because farming speed is not a priority of mine. I agree with Kram about Armiger, and I'd recommend Soulbond Bowyer, as well. 

And don't sell your roster short, between Stag Knight, MM, UDK and Coldheart, you have a very solid general lineup for most dungeons. 

Armiger and Khatun sound like two great options as your next two champs to build. Armiger is especially enticing as you can book him with dupes you buy from the market and is an excellent TM controller. :)

On top of the above advice on HK/Armiger, HK can function quite well - especially in an Arena setting - without books. :)

i maxed HK almost as soon as ive got her. never regreted it.

Thank you everyone for your suggestions. I will see what I can do with High Khatun to make her faster and more resilent. Also, I've been grroming Armiger and Soulbond Bowyer slowly. Maybe it's time to speed up their progress. :) It's really funny. I used to pull armiger often enough and used him as food. Now that I finally decide to raise him, just can't pull him any more. He is waiting for his skill upgrades quietly.

Thank you. I've been struggling with only two level 60 champs (Kael and Spirit Host) a month ago. MM, UDK, STag Knight and Coldheart were all great enhancement to my roster, I can't say I'm totally unlucky with shard pulls. :)