For a long time (before the 4th Air Defence) the All Dragon Army was a central feature of the game. An attack with all high level dragons can still be very deadly and although it has a high cost and long build time it is still a very popular army. Many people supplement their dragon army with a handful of Archers and/or Giants to take out exposed Air Defence towers before deploying the Dragons
Strengths and Weaknesses
The major strength of the Dragons+ Army is that they cannot be targeted by many towers (ie: Canons, Mortars and Ground targeting X-Bows) and hence they can last longer and do more damage. They also have a great balance between high damage and high hit points and there is no need for meat shielding or tricky deployment strategies. However they do have a major weakness in that high level Air Defence towers will take dragons down really fast
Bases to Target
The only thing you need to look for are bases with low level or exposed Air Defence towers. However watch out for Inferno Towers as well as they will take dragons down at a reasonable speed too. Even high level X-Bows set on air targeting don’t take dragons down particularly fast – however combined with Air Defence or Inferno towers they can cause a problem.
If you have additional Archers and/or Giants then use these to take out exposed Air Defence towers first and then drop your dragons closest to the highest concentration of Air Defence to try and take them out fast. Use Rage or Heal spells to make your dragons last longer. Some people like to spread their dragons out to protect them from High Level Wizard splash damage, however personally I find they are better clustered together because they take down the air defences faster and are easier to use spells on.
Watch out for!
The major problems for the Dragons+ army are high level, well spaced Air Defence towers and Inferno towers. Air Mines can hurt the Dragons but due to their high cost you generally won’t encounter these until the much higher trophy ranges