Luck, probably. I've got quite far in the Fighters guild, that might have something to do with it. Weaponry is my problem. I'm still trying to find a decent two-handed sword to replace the dai-katana I got from the Blades monastery.
Oh, it's pissing me off immensely. There's nothing more annoying (aside from lockpicking) than having your sword run out of charge midway through a big battle. Trouble is, I need the extra 15 damage to have any chance of victory.
That's Ebony armour. I looted it off some Blackwood mercenaries while on a Fighters Guild mission. It was just after I made Champion. It's good stuff. I think the cuirass is 14 armour.