Defending Gyarados
Answers
Congrats on the excellent move set! Power him up.
On offense that moveset will be solid against Dragonites. Although though he probably isn't the best Pokemon choice, battling with Gyarados is awesome.
On defense that moveset will punish Dragonite's who battle against you. Although your Gyarados will still almost certainly lose it will put a big dent in that Dragonite. It's also a good all around defender moveset because DT is a nice slow move with high energy output that the AI will use well, and O is a hard hitter which will punish anyone who misses the doge.
The DT/O moveset is extremely powerful in general. Good all around damage output with good energy output.
EDIT: My comments might seem negative but the reality is Gyarados is a fraud in Pokemon Go. Very high CP with good attack stats, but still pales in comparison to Dragonite in every category.
Yes. And there's the major flaw with the irrelevant CP stat. For defending the only thing that realistically matters is CP. You want your guy to be at the top to last the longest and avoid same team cannibalism of the lower spots (unfortunately). True that a gym full of Blissey's and Snorlax's is a psychological deterrent, but the better strategy is to let your fellow team mates handle that and toss your 3K whatever on top of their hard work.