[cryptana]

Shadow Priests are tough, no doubt. Remember though that they only have a single fear, on a 30 sec cooldown, and it's AoE, so if you stay away from the priest, they can't cast on you (although they can cast on your pet). You don't say what race you are - I'm undead, so I've got at least 60 secs of effective fear immunity between Will of the Forsaken and the PvP trinket, but your mileage may vary. If your opponent isn't undead, you can just fear-kite them into oblivion.

A good priest will dispell your buffs and DoTs and also cast Silence on you, so the advice above was valid (stick to Amped-Curse of Agony and direct damage, try to spell lock their shadow spells when they cast Mind Flay, and save your second Spell Lock and/or Death Coil for late in the fight when they are trying to heal). I also agree with siccing the Fel on him - both to slow down/interrupt his casting, and as a nice 40+DPS dot. Corruption is not necessarily useless (if they are dispelling it constantly, you can spam the rank 1 version to trick them into wasting mana/cooldowns on unnecessary dispells), but you can't really depend on it as a source of damage. In your case, it sounds like the priest wasn't even dispelling your Corruption, in which case you should feel free to load him up with DoTs. Does anyone know if a priest can dispell Drain Life? If not, then drain tanking seems like a reasonable action too.

I'm demonology spec'd, so I don't tend to have too much problem with casters of any stripe (with the Felhunter out, I have a minimum 1 in 6 chance to outright resist any spell, plus a good chance to partially resist any damage even if the spell lands). Plus with Soul Link I have an effective 4000 HP (more if you count Shadow Ward and my improved Healthstone). This isn't to brag, but just to say that some builds aren't as effective against shadow priests, and I'd say that a DoT-reliant build like your typical Affliction spec is going to have problems with a class that can dispell and out-heal your DOTs.