I recently played my first two Cityfight games. First game I took a WWP army with a Haemonculus with Grots on a single raider. Big squad of Wyches, Warp Beast pack, two larger Warrior squads and a Talos to come out of the WWP. One Mandrake squad, one sniper sqaud and a 10 man / 2 blaster "mobile sniper" squad. This army was very effective.
I also tried a more "traditional" DE list, Dracon with 5 Incubi on raider, wych squad on raider, warrior raider sqaud, 2 sniper squads, 2 ravagers with 3 dis, 5 reaver squad with 2 blasters and succubus, tooled out Archon on reaver. This army also performed well.
I think that some of the less useful (or more difficult to use depending on your opinion) units can be more successful in Cityfight than in regular 40k. For example, Warp Beasts, Grots and Mandrakes benefit from the abundance of cover. Wyches on foot can actually be an option in Cityfight, even without a WWP. The big thing you have to watch out for is flamers. They can really ruin your day and since most other armies can have an abundance of them compared to DE you gotta be careful, nothing worse than assaulting your Wyches into difficult terrain and falling short only to have the whole squad wiped out by a couple flamers the next turn.
rupract