Got pretty mixed feelings towards this update as well. Rather turning positive over time though.
I think the protection thing makes a lot of sense, since it disables characters as Rey or QGJ to one hit serveral of your squad members to pretty much decide the battle before it even started. Yet, combined with the huge changes considering the damage-speed relation, it is too much. I dont want to deny that characters as Doku or Sidious were op, being the reason for most players to put them in their squad, but yet you shouldnt have made that hard changes to them. I would rather keep the protection, but move the characters back to their old stats, dealing the same damage. In that way the effort you put into farming their shards wouldnt be gone, since they still would be valuable squad members.
So all in all I like the protection, but dislike the change to the characters stats, since it would have been better balanced by only adding protection to avoid 1 hits and by that enabling new strategies to be used in the squad arena.
Concerning the challenges I agree to what probably the most of us say: They are to hard. I liked to start on challenges by doing them manually and once you got your characters on a decent level autoing them. Playing the same all over again manually gets boring pretty fast and the use of the auto function made great sense in the challenges, in my opinion.
To summarize I guess I liked the update, yet the huge change of stats appears as a no-go to me. On the other hand I consider the protection as a great thing. Well, challenges should more a incidental thing to do and not something you really have to spend your time on, we got GW for that.