I thought the lightsaber combat in this one was much better, too. I know that's been a complaint.
Ahsoka is probably as hard to port to live-action as Yoda would be. You watch her lightsaber combat in the Rebels or Clone Wars cartoons, and it's a whole other level beyond what they're able to show in live action.
If you watch the lightsaber combat between Ashoka and Anakin in the Clone Wars temple fight, especially, and you see her doing things athletically that you just can't make a real person do without a Matrix-style approach to combat, and that is costly in time and money.