I changed my Champion to Samurai.
Fighter Samurai (lvl15)
STR 20 / DEX 10 / CON 16 / INT 10 / WIS 14 / CHA 12
Feats. HAM, GWM, Alert.
Skills. Athletics, Stealth, History, Insight, Perception, Persuasion.
For a Fighting Style I choose Defense. GWF is ok, but don't give you a better damage, just a consistent damage. On the other hand, Defense gives to you a better AC than you expect have.
When you don't need spend a feat for Resilient on Wis, you can have other great feat for your character. In this case is Heavy Armor Master.
The only drawback with Samurai archetype is Fighting Spirit reset only on long rest. Give it two uses and reset on short is better than this.
My actual dilemma is:
1. 20 CON on lvl 20 - 224 HP +11 CON save;
2. 18 and Sentinel - 204 HP + 10 CON save and reaction attack;
3. Tough and Sentinel - 224 HP + 09 CON save and reaction attack.
Well, technically, GWF gives you a good chance at more damage but I agree that if you only have your weapon dice, it's of limited effect. A Battle Master, however...
Depending on your role, I would choose #3 in a heartbeat, being a sticky tank is always nice.