SD Landorus can potentially destroy this team. Fortunately it doesn't get many opportunities to set up, but if you get caught off guard it can get +2 and OHKO pretty much everything from there. Since it's immune to Toxic Spikes, you won't be able to wear it down. You'll need to fight to keep the enemy hazards away, so that Forretress can maintain full HP for Sturdy so it can hit it with Gyro Ball. Although Virizion outspeeds Landorus and resists Earthquake, with sandstorm up it still takes 85-101% from a +2 EQ, so there's a good chance of an OHKO with sandstorm damage factored in. Since you outspeed it, you can hit it with a Leaf Blade but it won't do enough to pose any serious harm to it. Without replacing anything, a solution would be to add HP [Ice] on Virizon and change it a Work Up set, although you'd lose a lot of overall power. However, a better solution may be to replace Jellicent with physically defensive Rotom-W, although that would exacerbate your already existent Terrakion weakness.
All of that aside, this is a brilliant team. Definitely one of the most solid examples of balance that I've seen for some time. Hence, I have nominated it for the RMT Archive and given it a Luvdisc.