Firstly, I love the rumbler. Feels amazing. Sounds amazing. Does good work.
That being said, there are three things I want to say about it.
1: The most important suggesting I have is to lower the bounce intensity on the grenade after it hits an enemy. It often goes flying just far enough for the initial target to be considered at a far distance from the blast, and take almost no damage from that blast.
2: inspiring barrage is a blessing that doesn’t make a lot of sense on it.
3: It could use some better blessings in general. Maybe a couple that change the grenade type, like shrapnel (for bleed) or firebomb (similar to the bomber’s grenade).
There are many other blessings for other classes’ weapons that would make more sense here.
The only very situational useful blessing seems to be Adhesive charge, I propose it stick to all armor too, or at least carapace.
Shattering Impact is broken (by design?) and only applies Rending to direct projectile hits, not AOE splash.
Limited to these blessings:
Adhesive Charge
Your Grenades stick to Monstrosities
Gloryhunter
+4-10% Toughness on Elite Kill.
Inspiring Barrage
Repenlish 10% Toughness over time during Continuous Fire. Stacks up to 5 times.
Pierce
Special Attacks ignore Hit Mass Bonus from Armour.