my dragon type Pokemon are
hydriegon lv 75
flygon lv100(my only non legendary lv 100 lol)
garchomp lv 71
dragonite lv 65
haxorus lv 64
and for some reason a Black Kyurem lv 79
In-game, it doesn't matter if you have a Dragon team or not, but Dragons are exceptionally strong. Synergy is a little factor as in-game is just about blasting through the opponent's Pokemon.