I used peacebringers and occasionally close range skylords as Masari
Told U for Novus
As Hierarchy I kill Walkers with Orlok's siege and Phase tank mobs, plus science walkers (3 cascade reactors on horns, 2 range increase thingies, and 1 weapons accelerator) with some saucers in both modes for support/AA and lost ones for AA fire
I feel that's not the best way, the best weapon against a tank (in this case a walker) is a better tank, right? (in this case again a walker) (old Soviet doctrine)
Dex, I play the masari campaign and I turtle and 3 walkers attack my base fully configured after like 10 minutes, detected them with Oracle (radar) and sent my 7 Peacebringers to meet them en route to my base almost every time and most of the time they all die in the same spot and don't even come CLOSE to stepping on even my outer fringe structures (btw: back then I hadn't learned to use Matter Engines for landmines yet)
Walkers are ridiculously weak in lategame, the Hierarchy really should get some tech structures so they can get better hardpoints.
I attacked a masari basse with 3 fully configured walkers, DEFCON 1 on 8 player map with 4allies and 3 enemies, all 7 easy AI and I lost all the walkers, but flattened te enemy base and my ally wiped them out a moment later.
Walkers need some beefing up towards late game, seriously.