All out.
Higher lvl you are, more things you open up. This includes character shards that you can farm. I just got barress shards opened tonight to farm which is something Ive been waiting for.
As far as GW is concerned. After about fight number 6 you'll always start fighting people higher lvl. When I was 53 I was fighting 60's. I never could finish a GW because of this. Now I'm 58 and have no issue in finishing GW.
Finish GW gives high amount of credits, and that's a very good thing at higher lvls as it takes 50k+ to get them 1 lvl. To get sid from 6* to 7* cost 1 mil. And I get around 1.4k GW tokens after a clear. And seems you get a character shard from one of the last characters you face in the last battle ( I got a Vader shard today and was really happy getting that ), because I have gotten a shard the last 2 days from this and always a character that was in the last group.