What's a good weapon to pair with a Heavy Flamer for a Crusader?

[Cosmo]

So i started a Assault Crusader, but i ended up going with the Heavy Flamer, I play on +3 diffulty level, and im doing fine...

But when i run into the Nurgle Harbingers i struggle with them, and the best weapons i found to counter this is either a Shield + Chain Sword, or a Heavy Bolter and its still hard.

Are there any better alternatives for a 2nd weapon setup?

[Schalimah]

Socket an Ordinatus Psalm anywhere in your gear and pick up the passive that disables HP regen when suffering from a DoT in the DoT tree.
This passive is almost mandatory in season 6.
This should help quite a bit.
If you build it right, you never need a second weapon.
I usually use the second set for Loot Quality/Quantity quick swap.