I'm not even sure where I'd start with a Quillboar nerf. Just... too good synergies. Dynamic Duo feels too strong. Agamaggan doesn't feel quite as crazy, but depends on your build, I guess. Same stat growth effect as duo, doesn't increase Duo's scaling. Flat tusk feels relatively weak compared to others (banner that does 2 at EoT, this is 3?). Charlga is nuts topend, but it's a 6, that's fine. Brute scales a bit better than it should for a T4, had some very big ones of those. Bannerboar feels pushed at three - a reliable activator with two per turn. Compare to Thorncaller. I'd look at tweaking Brute and Duo, probably, maybe banner (+2/+2 in stats per turn on a 2/5 feels very good compared to other stuff).
Golden Bonker is... Bonkers. Shouldn't have mega-WF along with the 2/attack - I overfilled my hand with bloodgems last game due to Illidan with golden bonker meaning 16 gems if I had enough space, and ignoring the golden frenzy that didn't get to attack... Turns out an early duo into seven gems on something else is just not really beatable (goldened a prophet - activated two prophets that turn with a frenzy guy, trebled prophet, got a duo which procced the golden prophet, and had a few in hand from previous - good turn). Felt like the easiest win ever.
Just ran into my first all Quilboars with golden Bonker, golden Charlga, golden Duo opponent. That taunt gets BIG.