I tried a Guts deck the other day and it was actually decent. Guts cards have tons of + Energy events it seems so I could train a lot. I still lost because my cards were not leveled but if they were all leveled up I think I could've won this relatively easily.

I tried doing Bakushin's campaign while ONLY raising Guts. My Guts cards were all level 1 and she got 7 Sleep Deprived (Including a night owl) so I got kinda cucked but with maxed cards and better RNG I think there is potential. What I've noticed is that ALL my Guts cards gave Energy every single event so you can apparently save a ton on rest time with those.