Interesting thing about Hydreigon, people say its outclassed by Latios, but standerd Hydreigon (383) actually has higher SPATK than standerd Latios(359), since most Hydreigon run Modest due to his wierd speed tier, and most Latios run timid. For this reason, I like to run a Modest Scarf set on my team (3 dragons) as an enemy dragon counter, using Modest instead of Smogons advised Timid for the power boost over the ability to outspeed Jolly Scarhaxor. Draco Meteor, Fir Blast, U-Turn, Focus blast and bam, you are Faster and stronger than Latios, with the upside of not being stopped cold by Ttar and Scizor.
Only real downside is that you're locked into one move