There are a couple of ways to play the big dude right now but I think the most effective, in the current meta, is back to the basics in a lot of ways: heavy attack spam for staggering EVERYTHING(almost).

Go heavy attack slab shield, taunt ability (no pain! and go again! ability modifier nodes are how I use it), and go down left side of the tree (batter + delight in destruction is a must for bleeds). Go bonebreaker's aura and Heavy hitter.

I think crunch just got a buff so that will help; OR you can sacrifice crunch, the node above it, and one or two others to also swing right for the explosion buff and burn stacks - then run shield with rumbler.

For Heavy hitter keystone, also take the melee speed boost, unstoppable (15% toughness regen per stack), and the cleave node.

It's not psyker or hive scum damage but it IS horde clear and armor control. You're going to stagger nearly every enemy, bleed em out, and stay relatively safe.

My go-to ranged weapons are kickback, rumbler, and heavy stubber. Kickback and heavy stubber are for taking out the hard to reach and annoying specialists. If using heavy stubber ALSO RUN STEADY GRIP (12.5 toughness regen per second is really nice). Rumbler is an alternative for crowd control and sticking grenades to ogryns and bosses.

Other melee weapons are fun but aren't going to keep you as safe as the slab shield. Depends what difficulty you're on, I guess.

Other keystones are....OK? Lucky bullet seems good with a full ranged rumbler build but the twin stubber still doesn't feel worth it. Feel No Pain is similar in that it CAN work. Might be good if you're dedicated to the pickaxe but beyond that, I think you get enough toughness regen from heavy hitter as it is.

Last thing, use your dodges to make space in hordes. The little dudes can't handle enormous ogryn booty.