Powering up new defenders

For me, one of the most exciting things about the gym rework is that we finally get to use the actual best defenders to defend gyms (although my city's gyms are, for some reason, still filled with Rhydon and Gyarados).

So I'm now considering maxing out some new and fun defenders, while keeping my high CP powerful mons as attackers for raids. These are my options:

Steelix, DT+HS, 84% IV, level 20
Umbreon, FA+FP, 93% IV, level 26
Donphan, C+PR, 87% IV, level 20
Arcanine, S+WC, 93% IV, level 26
Tentacruel, PJ+SW, 91% IV, level 27
Poliwrath, RS+IP, 82% IV, level 28
Slowking, C+B, 89% IV, level 20
Muk, I+SW, 73% IV, level 20

Feel free to share any suggestions! I have about 200k stardust atm.