Slitherine

So, I am at Acheron mission. It looks like it is the last one and I just need to survive 'ill Space Marines save me. However... I cannot ;/

My current army consists of 3 basilisks, like a 5 medusa, 6 fire support, 2 salamandra scout (great firepower + scounting for art for 200), 3 Leman - Ann - A, saved rocket launcher guys.
Everything goes very well, I start to retreat after turn 4, near turn 10 almost everyone is alive, orcs die... then 3 Skullhammer battlefortress come and ruins me. This mega-thing just vaporize my army. Only basilisks can safely damage it, however it takes ages. I've tried to use 6+ basilisks, but they lack medusa power and their price is higher, so near turn 10 my army is weared and tired. At some point (near turn 12) orcs just overwhelm me. My army toughness isn't the issue - damage is. I just cannot destroy all these pesky orcs units, and they snowball. They brings it artillery and mobile zappa cannon, warbosses reveal maps for them...

...
I am desperated
Any advices?

Maybe you have the wrong army composition. I often use destroyers and anti-tank teams when I want to wreck skullhammers. one or two hits and they are weakened. several hits of these and they are toast.

There is ton of orcs beside these fortresses... did you manage to win Acheron with destroyers and aanti-tank teams?

Ok, I've done it... that was a pain...