Hyper Offense wants to avoid Choice items. If you lock yourself into something the opponent can force you out all too easily which essentially means wasting one turn of your Screens and giving them momentum. Hyper Offense also generally uses 5 attackers, mostly set-up sweepers, of either Physical or Special, but not both. The idea is that your opponent probably only carries one dedicated wall to a certain type and that if you can simply overwhelm it the surviving members of your team can easily clean up afterwards. It's not unheard of to put yourself in a 6-2 or even 6-1 or 5-1 hole and it's also perfectly fine as long as that 1 can finish the match for you.
While I agree with Thundurus-T over Raikou, I feel like I have to point something out here. Just because something isn't OU doesn't mean it can't be used in OU. Look at Amoonguss. Or Xatu. Or Claydol. Zapdos, Zoroark, Galvantula, Rotom-H, Rotom-C, Chandelure, most Trick Room abusers and Pokemon like Shiftry who can abuse weather are all great examples of lower-tiered Pokemon that do great in OU given the right team.
Considering that it isn't in OU, you might want to consider the OU options.
"Whether Castform the Weather Pokemon can weather the weather is dependent on whether the weather that it's weathering is the proper weather for it to weather. Whether the opponent can weather the weather is also subject to whether the weather that it's weathering is the right weather to weather. Whether Castform can weather the opponent is once again dictated by the weather and whether that weather is the favorable weather for weathering. But most importantly, you should know whether there will be weather to weather rather than what weather they will be weathering and whether they can weather that weather."
- Smogon's Castform analysis