Gyarados... I honestly haven't seen much of it recently, so a lot of what I'm about to say will be theorymon. There's no doubt that Gyarados is one of the most underrated threats out there. It can most definitely wreck teams with the proper support. The question is really how much support does it need to be effective. Gyarados is sorta stuck on Rain teams, since Politoed does quite a lot for it, being able to remove sand and hail that would chip away at Gyarados, while at the same time boosting its main STAB. Then you need something to spin for it, which pretty much leaves you with either Starmie or Tentacruel (or Forretress, if you're ballsy enough to run that in rain). Lots of similar typing there. After that, you need something that can handle Ferrothorn, which beats basically everything I've mentioned up until this point. And at this point you've got 4/6 members of your team supporting Gyarados. I just think that Gyarados needs more support than some other options. Not saying its bad, but that it does need quite a bit of support, and therefore is difficult to fit into a team.