I have no idea what gear you're wearing for a 3800GS, as I've completely ignored the whole GS thing because I raid with people I like instead of going on pugs that demand I dress to fit some arbitrary number ...

... but 1kdps at 80 probably means you're doing something wrong, even if you're trotting around in freshly crafted tempered saronite blues.

Nuggets of advice from a protection warrior who's been known to top 15k DPS on ICC trash packs:
- While Heroic Strike and Cleave are on a mutual 3s cooldown, they're NOT attached to the global cooldown at all. Use a macro collection to automatically cast one of them whenever you use any of your regular global-cooldown abilities. I macro in a /click command to make my macro click a particular slot on my action bar, then drag HS or Cleave into that slot depending on which one is right for the fight.
- "Tanking" weapons (fast, +str, used to have defense on them) are weak right now due to changes in how the overall prot damage output interacts with swing speed. Grab one of those slow one-handers that are meant to be for combat rogues and enhancement shamans. Yes, the ones with agility. If you can find one of the rare ones with attack power instead it'll be even better, but just the high base damage on a slow agi weapon will supply a good chunk more damage than an equal-level fast str weapon.
- Pop shield block as you start the fight. Your shield specialization talent means 15 rage per blocked attack, so if you charge into a pack of 5 guys with shield block up and they all swing at you once that's 75 rage straight off the bat AND it buys some ramp-up time for the healer by reducing your incoming damage. If there's a caster in the group you should also bring up spell reflect early because you'll get sixty rage off a successful reflect.
- Don't try to open with a rend on a multi-target pull. Somebody (healer or DPS) is going to cast early and take everybody but the guy you rended (plus maybe his friends that you cleaved). If the group's positioned so you can hit them all with a shockwave, open with that, then rend and thunderclap while they're stunned. If you're opening with a shockwave then you should save your shield block for when the shock wave breaks so that you're not standing there wasting block uptime against targets who aren't swinging at you anyway. If the group's spread out wrong for a shockwave, hit them with a thunderclap straight away without rending, then get a rend in in time for the second thunderclap.
- Priority for the basic attacks is shield slam > revenge > devastate. There may be times when your revenge seems to hit harder than shield slam, but you should still use the shield slam first because there's a good chance that the revenge will proc sword and board and light shield slam back up. "Shield slam, revenge, shield slam" hits harder than "revenge, shield slam, devastate" and probably costs less rage.
- It's bad when your attacks don't land. Gemming and reforging to reach 8% hit and 26 expertise is a good idea. Going over 26 expertise isn't OK if you're raiding because raid bosses have bonus parry chance and the extra expertise will continue reducing that.
- This one's going to be controversial, I'm sure... Attacks not landing on you is also arguably bad, as taking damage supplies you with both rage and bonus attack power. Once your dodge+parry hits 35% (for 5 mans, or about 45% for raiding) you should look at reforging some dodge or parry into mastery for more block chance. Block means you take partial damage so you still get some rage and bonus AP out of it, and you get the 15 rage from shield specialization thrown in too.