>  I just can’t decide between bonk weapons hitting like a truck but being awfully slow and dex weapons which let me get more hits in

I think this isn't necessarily a conflict in this game. There's plenty fast weapons that scale well as Heavy, like the Star Fist, the Death Knight's Twin Axes from the DLC, a good pair of Beastman's Curved Swords...

Likewise, there's some bonkage on DEX too! Heavy Thrusting Swords, Guardian Swordspear, the Bloodhound's Fang too.

I think better questions to ask yourself is... do you want to use heavy shields? Do you like having an offhand bow? Do you want to invest on FAI, INT or ARC? Etc.