Well after a few more tests, I decided to change Latias' moveset from 3 Atk/LO to Choice Specs. Its sheer power and Trick really helped this team. Thanks for the suggestion undisput3d, and everyone else:
I don't see the point of Taunt on Tyranitar since it is slower than most OU leads. I realize Avalanche is unorthodox, but it has really helped deal with certain leads. I wanted to use Ice Beam but that would force me to use a -speed nature, thus losing to opposing Tyranitar. Ice Punch is redundant since it has no use outside of 4x weaknesses, and Stone Edge's shaky accuracy is a real put-off for me.
I don't really want to change Gyarados' spread to a SDef oriented one because I need it to cover physical threats like Salamence and opposing Gyarados. Gyarados' current spread means it is never OHKO'd by Salamence's Outrage or Gyarados' Stone Edge after Intimidate, but it will be with the SDef spread.
Ice Punch on Metagross has really helped with Gliscor, Flygon, and Salamence switch-ins. Zen Headbutt doesn't really cover Metagross' common switch-ins. Swampert doesn't bother Jirachi at all. It 3HKOs it, meaning Jirachi can alternate between Wish and CM/attacking if Swampert doesn't Roar it out. Psychic does a considerable amount of damage to it anyways.
DDTar can be a problem if Rotom-H goes down or tricks away its Scarf too early. In the past I have been able to play around it with Trick and Gyarados/Tyranitar's Low Kick which is why I haven't really considered it as a major threat. Scarf Tyranitar, however, is annoying because it outspeeds everything on my team except Rotom-H (which isn't going to do much to it anyways). Specs Latias has somewhat helped this weakness since most people do seem to send Tyranitar in as soon as they see Latias, allowing Surf to take a chunk off of its hp.
I really don't want to replace my Tyranitar for Swampert because it doesn't do much for this team. Tyranitar is a very valuable team member for the reasons I listed in its description. Swampert is a less reliable lead (in my opinion) and really doesn't cover any new threats that I don't already have covered, besides Scarf Tyranitar.
I have a small suggestion on Latias, I used to use Life Orb as well but I've noticed that Expert Belt works just as good.
Latias @ Expert Belt
Nature: Timid
4 HP / 252SpAtk / 252 Spe
-Draco Meteor
-Hidden Power [Fire]
-Grass Knot
-Surf
Bluffing the specs/scarf has won me quite a few wins (:
I will have to test this set a bit more. So far I am preferring Specs since it has Trick and much more raw power. However, this set does catch people off guard which is always nice.
The problem I have with Magnezone is that it doesn't do much for Jirachi. Yes, CB Metagross can be annoying but Gyarados is usually a safe switch-in to it, bar Explosion. Heatran is the biggest Steel type threat to Jirachi and Magnezone isn't going to help patch that.
I switched Latias' set to Choice Specs so it now has Surf, meaning it can actually damage Heatran now.