Wow, thanks! Good to know I can rate a team!
I don't like the look of Golurk. While it's base stats say otherwise, it seems "squishy" being outsped by most things and hit for SE damage with all the Water / Dark / Ice attacks being thrown around in VGC. Gyarados looks a tad better, but it's been underwhelming for me. Maybe something to test, but I can't recommend it. However, now that I've had a second look at your team, there is one Pokemon that might fill in the last slot pretty well.
Special Attacking Salamence offers you the same resistances that come with Dragonite, but comes with greater raw Attack stats and Intimidate. It might seem repetitive with Latios, but Heatran's frying any Steel-types in your way and you don't have to use both for a battle. Sure, it can't KO Cresselia, but it can dent it and Heatran's walling Cresselia all day. I guess my advice for tyranitar was kind of haphazard ignoring the Fighting weakness, sorry.
Hope this helped!