Why isn't Krennic/K-trooper used more in the arena?

I run zzThrawn (L), Tarkin, zDT, DK, Shore, and it's a beast of a team. However, I went hard at DK when he was in shard shop, and got him from whatever we had at the marquee event to like 40/100 during his limited run there. DK is a hard farm, is squishy even at 7*, and requires you to have a zeta on DT.

Under a Rex lead, he's less useful than other options, and if you're running any variant on a hide-the-nihilus team, he's definitely not a great option. For a pure empire team, he's solid as can be.