Dragoons can be easy to kill when you know how, with big hitboxes they are easy to hit, but unfortunately they can pounce away and get to safety. Personally my favourite weapon for this job is the humble chaingun.
My FAVOURITE weapon it can kill anything, dretches, basalisks, maras, goons and tyrants. Once you have perfected 'dueling' you must learn to duel with a chaingun. Against a dragoon this is lethal, as they loose life quickly and cannot hit you back. However it can fall short to one weapon, the not as humble, but still humble, painsaw. This baby can kill anything!
Excellent for countering an alien rush.
The chaingun eats ammo quickly. Aliens love to munch a defenseless chaingunner trying to run back to the base.