So how much ORVR does it take?

To max out a tier.. I did 2 keep raids last night and the meter barely moved lol


Also how do the epics work, and the blue rewards what determines whether you get either?

Well, if you're just taking empty keeps, it's going to take quite a while. I think they're worth 450 inf(?) and you'll get a couple hundred more for flipping BOs if you wait the timer out.

Now actually defending or attacking a defended keep...you're going to get a lot more XP, renown, and influence. But usually people don't want to do this because it doesn't result in immediate gold bags and they may have to PvP instead of kicking the crap out of a door.

Not sure what you mean by your other questions. Rewards for a keep-take are determined by player contribution (read: random roll).