I just got Maxx so maybe this is WAI, but it seems dark summon only works if you target a space within the deployment zone. Otherwise it takes 3ap, goes on CD and nothing happens. Since his fatass takes up so much of the deployment zone anyways, it seems like he should be able to deploy something 1 square outside.
I thought he used to be able to summon them anywhere. Did you have a 2x2 available to summon? 'cause I know there's issues with that.
I had plenty of 1x1's available for it to choose. I tried 2x outside of deployment zone and nothing happened. Tried in the zone and out popped a champ.
Remove the 2x2 champs and try. Funny thing I don't have him because meh, I don't like champs that don't move and that's another reason I don't use shadowrake that much.