Please implement anti-sandbox functionality
We have all been there - watching replay where enemy is attacking our village in clan war, having only heroes and flying troops except a single goblin. And right in the end when their lava puppies are after my ground skeletons they deploy goblin in far edge of the village, my skeletons follow and puppies chasing right behind them. And after skeletons are out, puppies will now take care of low-hp buildings just to reach 50% and 2 stars.
You just got owned by a sandboxer.
First of all, I do not know how the game works here. I do know something about other real-time gaming (for example online poker) and how they are dealing with public and private information. I haven't been analysing data traffic (I'm way too lazy) thus I might have one or few (if not all) ideas wrong here.
Problem with CW sandboxing comes from the way how information in CW is delivered to the client: all information including CC troops, traps and tesla locations are given already when you click scout - you can see there is no latency when you hit attack so information must be on client already.
Now, sandboxer has cut the connection and somehow mocks server connection to his client thus game lets them attack - but SC server does not get any indication from this happening. Basically they can practice attacks until they find best achievable result, and only then let client to get back in talks with the servers.
As temporary offline gaming functionality is a must-have (for example when you lost network connectivity for few seconds before reconnecting) I would suggest modifying the data sent to client being split in two: public and private part. Public is what you see when when you scout the village. Private is data that has to be revealed for the client (but not necessarily GUI) at some point in the game.
Now, when you would be scouting the village you would see exactly the same you do see currently. Only under the hood client would not get information of CC troops, traps, teslas and so on. When you would hit attach, client would request this data from the server - and therefore also using one of player's attacks and option to this village.
As a side effect you couldn't cancel your attack anymore if no troops have been deployed. Not too nice but given current horde of sandboxing it's not exciting to go for wars anymore. In my clan (45+ players) only 20 tend to opt-in for clan wars after we had 3 sandbox clans as enemies in row.
Of course we cannot be certain they were sandboxers and we'd just lack the skills - but replays of their attacks just seem to be a bit too perfect. Our top villages get 3* hits on first try with perfect troop selection against our CC holdings, and somehow those barbarians were deployed on top of traps before wizards came in hands blazing.
Probably this sandboxing also affects non-war battles as well but it hasn't manifested as big problem for myself or my clan members - at least not yet *knock knock*.