5-8% toughness on Chained Hit.
Target receives 1-4 Stack(s) of 10% Impact if already Staggered. Lasts 5s.
Special Attacks gain +10-25% Stagger and ignore Hit Mass Bonus from Armour.
This build abuses the fact that all special attacks on Ogryn count as heavy attacks.
By using the Rumbler, you have access to the fastest attacking heavy attack that has good cleave.
Pair that with the feats that bleed on heavy attacks and replenish toughness on heavy attacks that hit multiple enemies, and you basically can regenerate 20% of your toughness while permanently having the 50% toughness damage reduction from your other feat.
The slab shield is interchangeable but since you will be meleeing primarly with the Rumbler, the shield has the most use to block snipers or anything too scary.