-your No. 1-5 problem is Rocks. Also, Roost is great. Knock Off is also great. These are the two last moves battling for the last slot. U-Turn is just awesome! You just spare one of your most important Pokemon a hit (unless you're faster). Don't drop Turn. And prefereably keep KO, since Items are really important to leaders and you'll do a lot of crippling that way.
-speaking of rocks: Magic Guard Reuni! Regenerator is good mostly for singles, but then again, MG lets you absorb all kinds of status, not care about Rocks, or Spikes, and also, no LO Recoil! In TR, you hit like a fat, blobby, green, hideous version of LO Alakazam! Also Flash Cannon is bad. You kill Ice with Focus Miss + Bullet Punch + Bird anyway. Ice is your last worry as a defensive type. Also, without Shadow Ball it gets walled by Doublade, Sableye/Spiritomb, Aegis. Doubs gets crippled for good by Knock Off. Sableye and Spiritomb die to Sylveon. Aegis, you can WoW it and then Flare Blitz in a turn when it can't use King's Shield. Unless they hax you. WoW first in any case.
-you can always spare 44 EVs from Def to give them to Sylveon's SpDef. I have played against that spread. Was super-annoying. Also you gotta keep Wish for support. Its coverage moves are far weaker without Stab Pilixate backing them. Just support your main stuff.
-also, standard TankChomp EV spread over that maxing out you've done if you want the defensive variant, or just go max speed and attack for some monos. Say, Ice. What's TankChomp gonna do there? Or Max HP + Att for TR. Or whatever. You have options.