How does the Electro Dragon chain is drawn over the buildings? Does it have a pattern? There's no much strategy if you span a bunch of dragons, but having one in the castle clan for a specific reason requires more accuracy.
The electro dragon's lightening will prioritize high health buildings. So every time the electricity chains, it will go to the highest health building within the lightening range. After the e-drag hits a building, it will chain four times if it can (if there are no buildings in range to chain to, the chain will stop). Each time it chains, the damage it does is reduced by 20%.
The lightening can only chain across two structures if they are next to each other or if there is a one block gap. So, if you put all your buildings 2 away from one another, the electrodragon's lightening can't chain. That is one reason why a lot of war bases have gaps around the outside buildings.