There are odd things you could improve but really... don't worry if its just Emalon handing you your chips. He really does hit like a ton of bricks and there's nothing much wrong with how you're geared out. Just remember to use your debuffs - thunderclap & demo shout - and provided they're up religiously, you're not doing much wrong. I was in a PUG recently with a paladin who tanked Emalon10 with 24k HP unbuffed - so it can be done - just gets a bit scary!
You will be fine in Naxx25, honestly - it's really not that huge a step up. Go PUG and enjoy it - what's the worst that can happen?
Personally I tend to use Vigi on high aggro dps. I have done the 'swap' Vigilence thing on Patchwerk in the past, but that's about the only one I really felt it was worth it. Your mileage may vary.