So, I had a game against this guy with a Blaze merc list, got a re-match coming up so I need to see where I can improve.
I think he's practising for Steamroller, so of course the list is a cauldron of pain.

Blaze
Rocinante
Precursor knights (I think)
Gunmages
Gunmage UA marshalling a Mule
eEiryss
Anastasia di Bray
Harlan Phineas Versh (I think, dude with Quad-fire)
Madelyn Corbeau
Rhupert Carvolo
Forge Guard? (dwarves with hammers)

I have (literally):

eSorscha
Beast
Spriggan
Koldun Lord marshalling a Destroyer
MoW Kovnik marshalling a Kodiak
Demo Corps
Manhunter
Greylords
Widowmakers

Any advice? There's so many threats from so many angles. I don't have much in the way of range and don't have the hitting power his force does (though back-swing and thresher are good for anti-infantry counter-attacks, along with the sprays from the greylords).

The Mule out-matches the Destroyer thanks to the gunmage UA, has a bigger blast, higher RAT along with crit slam.
What can I do against this thing?
Maybe send the widowmakers/manhunter after the UA?

Shatterstorm and the widowmakers is a favoured tactic of mine (and just about all eSorscha lists/players), though against defensive line and shield wall it's not that effective.

He generally keeps the solos back behind the knights, meaning I have to get dangerously close with the spriggan/windowmakers to attempt to drop them, which then exposes them to the knights and dwarves. I can't swap them over to iron flesh as the former have blessed weapons.

I think I need to whittle his front line down with the snipers first early on. Plus at latter stages I could feint a large attack in order to get him to pop his feat and then pull back to waste the benefits he gains from it.

He is allowing proxies though, so any ideas what I could run things as? Perhaps swap the manhunter for a widowmaker marksman?

Possibly drop the manhunter and swap the DC for bombardiers? I have enough beat sticks, but not enough speedy or ranged anti-infantry.