haha, the banner is hilarious. Where'd you get it?
The reason why I think Poli and Ttar should both be defensive is because they are defensive on different sides. Politoed is extremely physically defensive, but has some trouble specially, Tyranitar is, in turn, extremely specially defensive, but also has some trouble physically. So they balance each other.
The main thing about your team was a lack of a defensive centerpoint- all of your pokemon had just one or two evs stashed into defenses. That means that moderately fast pokemon like Banded Terrakion would give you problems, because none of your pokemon were offense enough or defensive enough to handle it. Either way, that's just a quick suggestion. It's totally up to you ^^
I'm electrolyte on PS! I occasionally talk in chat, but most of the time I just battle, so I'm not voiced or anything.