Rotom-W, a single Pokemon is your only argument? (there IS no "etc" after Rotom-W, there are literally no other OU Pokemon that can switch in safely on a subbed Gyarados and threaten it that can't also do so to band or scarf). It's not like Gyarados is going to fare a lot better against Rotom-W with a choice item anyway. While you could destroy it on the switch with Band, Rotom-W outspeeds you and can take an unboosted (from choice scarf) Double-Edge and KO back, meaning Gyarados will have to switch anyway if it predict right on it coming in. I could use the same prediction with my current Gyarados to switch to a counter/check. This ability to hit Rotom-W on the switch is in exchange for depriving me of my status blocker, forcing my team to eat Thunder-Waves (Don't say Jolteon or Mamo Take care of that, they get pummeled by common T-Wave users), Toxics, Leech Seeds, etc, and deprives me of my single most effective sweeper. All because I'd lose 12.5% HP (Don't forget the 2 turns of leftovers recovery; I can stay in perfectly safely for one turn with that sub up) when Rotom-W switches in. Which is less than Bulky Rotom-W would take from even an unboosted Waterfall outside of rain with leftovers recovery. Oh, and if that Rotom is choiced like so many are, and uses an electric attack on that sub? Free switch to two of my Pokemon that love getting free switches!
The Gyarados I have benefits much more from the pairing with Jolteon because of all the set-up opportunities Jolteon supplies. It just so happens that most of Jolteon's checks are set-up fodder for Sub-Gyarados. This fact has led to Gyarados becoming my most accomplished sweeper and probably my all around MVP. It gets tonnes of set up opportunities and can take advantage of them like no other. This is unlike Band and Scarf Gyarados, which require the opposing team to be seriously weakened to sweep, and can very easily provide the opponent with momentum. There's a reason that Bulky DD Gyarados is the first set on the Smogon analysis (yes they are organized in order of prevalence, I've written analyses before).
Thereby I conclude that my team utilizes Gyarajolt just fine. It doesn't use it the same way band or scarf does it, but it's just as effective, if not more. Your argument about losing HP setting up subs on unfavorable switches doesn't add up because the opponent is always going to be getting the short end of the stick regardless. If you have any advice on how to address my team's ACTUAL problems (like the weakness to scarfed dragons, Stone Edge carriers and Starmie) then I'd be glad to hear those. What I don't need to hear is more pride based arguments because you can't get over the fact that you were wrong.