Dirty Bird
Pokémon Master
I was the same.One warchief gave me hell. Then after dying a few times to him he retreats to a new place. Stronghold with less baddies and more explosions.
Got through 2 easily.
1 I couldn't get to.
2 I could, but couldn't stand a chance.
Eventually I saw they leave the safety of the stronghold for 'celebrating' my death.
So I check their weaknesses, both have instant death from stealth.
They died quite quickly next battle.