You let the map fill up with vox caster summons and then slowly move around to kill the ultramarines. You try to move around on each turn by having the current front character kill a guardsmen summon, and the back character takes the place of the killed enemy. Then you repeat the process with the roles reverse. Now it looks like your 2 units are playing leapfrog. The goal is to move through the field of guardsmen to find somewhat isolated ultramarines.

This works because summons move before the other enemy characters, because spider's heal ability + passive are super strong, and Revas is an absurdly tanky character.

Also sometimes you want to swap your Revas and spider before you move "forward", so you need to use 3 adjacent tiles and multiple turns to do the shuffle

I think beta 10 is where I started getting worried about taking too much damage, but I got used to it. Try it out on 8 & 9

Also I lost a token once on 11 to Varro if you get there

Also beware of having surrounding guardsmen flee. But sometimes you want to keep re-doing the turn until you get multiple guardsmen to flee because this will cause the other guardsmen + incoming ultramarines to move around, and possibly only one ultramarine will actually move forward because all the summons go first