I'm an Oblivion fanatic! And I mean that in the literal sense, I've been playing Oblivion off and on for several years now and have beat every part of it tens of times(still never beat shivering isles). I'm obsessed with trying to get the perfect balance of performance, graphics, and mods thrown in. I've installed the game hundreds of times (I have to reinstall it every time I mess it up too bad with tweaks and mods:P). My characters are usually paladins(custom class not default ones) or mages or a combination of the two but I've played a couple assassins less successfully before. My current build of Oblivion is my best one yet, I used the newest version of FCOM 0.98 to combine aspects of OOO, MMM and Francesco's mod along with 70 other various mods and still growing. The performance isn't great but it's good on medium texture size with various ini tweaks and Streamline running all functions. The content and gameplay is perfect, slightly difficult when I walk in a sigil tower and have to fight 50 dremora but I handle it okay. My current character is a level 24 imperial paladin with the argonian companion from Ruined Tail's Tale. Anyways I got a little side tracked, I do apologize...
I'm serious when I say this: If you have any questions about Oblivion concerning anything to do with it, whether it be performance issues, mods,lore whatever, it would make my day to answer them for you, makes me feel useful,lol 
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"I don't think you're making any sense at all."
"My boy that's all I make, which is why I'm such a lonely man."