Continuously chaining more than 2 attacks gives 2-5% Power. Stacks 10 times.
12-24% Rending on Enemy Weak Spot Hit for 3.5s. Stacks 5 times.
Target receives 1-4 Stacks of 2.5% Brittleness on direct projectile hit. Debuff lasts for 5 seconds and can have a maximum of 16 stacks.
3.5-5% Critical Chance for every 10% of magazine spent during continuous fire. Stacks 5 times.
Shout and have a 5-10 second long burst phase where you hit things on the head and they die.
For Monstrosities, tag, open up with kraks, shout, then magdump the bolter into their face.
For Hordes, swing at head level with the shovel. Use literally whatever combo chain you want, they're all good.
Heavy -> Light -> Light -> Repeat is a fun one. Shovel has good stagger, dodge with every heavy charge and then let it rip to protect yourself while charging.
Use your alternate attack for Ragers. Heavy -> Alternate will stagger them out of their combo. Also works on Maulers and Crushers to a lesser degree.