Strategies:-
The Deava, a fast and agile fighter, though capable of defending and attacking, it needs the help of other units or it will die rather quickly. It also needs Cloak and at least a tech level 60 gun to fair well in the battlefield. In early stages, Deavas can help by assisting poc defenders or poccers. Because of their low HP and Armor, they are forced to flee when arbs are aiming at them.

Defensive:-
If you are an Education player and you have 120 EDU, get the H-Tommy Gun or the H-Fireball. These two weapons are very formidable and is capable of killing even the strongest units. H-Tommy Gun and Tommy Gun currently have no animation thus, if you cloak other a tree and you are using Tommy Gun, you can shoot the enemy, but the enemy doesn't know where you are. This is very useful in defensive battles that have choke points. You can hide somewhere near the choke point and attempt to take out as many units that come by. But chances are that you need a very healthy stock of energy or a coupler near by. Also, Deavas can be used to "raid" poccers using the Fireball as it does fairly great damage in a short amount of time.

Support:-
Deavas, as stated above, are support units. They aren't the kind to rush into an enemy territory and expect to live. Deavas can support slow but important units like the Arbalest or the Ballista from close range units. Deavas can also be put behind the front line to help assist in killing the poc defenders or the artillery. Deavas work best with cloak. If you have cloak and you are using Tommy Gun, and you run into a group of Pegs ( fairly low armored units in early stages ), you can just press S to stop and your Deavas will start to auto-fire at the Pegasus.