Spec: Drop Licheborne and Morbidity. Put the points in Scent of Blood and 2H Weapon Specialty. There aren't any fights in the first section of ICC that make great use of Acclimation. i would shift 2 points into Scent of Blood and 1 point into Hungering Cold. HC is really nice when someone pulls an extra group(which is a real possibility in Lower Spire with a pug).
Gear: Get the Triumph armor trinket to replace the Onyxia Blood Talisman. Your expertise is a little low and you are slightly over on hit rating.
Strats: There's not much to the lower spire. The boss fights are relatively easy from a tanking perspective. Just make sure to turn the cleaving mobs away from the raid. Use DG to pull casters or spiders into the AoE before Marrowgar. Don't get ahead of your healers and be patient. It is better to take a few extra seconds to make sure the pull is right than to wipe.
Stay out of the blue stuff on Marrowgar; if the raid is stacking in the hit box, you and your OT decide which way you'll start the "2 step" i.e. the blue ground crap will come at the tanks and they need to side step together, one or two steps that's all decide if you'll step left or right first.
Deathwispers, kill the caster adds first, don't buy into the the /magic on this type or melee that type (unless they're bubbled then melee burn the bubble and then everyone on it) single target them down with full force; the faster you burn them the more time on the boss (if it's 25 then magic on Fanatic melee on Adherent is necessary); don't stand too close to the big ugly swamp thing as you kite it (get a hunter to help) makes sure the raid ranged dps immediately burn it down it will one shot the world. On the boss make sure you watch for the DnD and interrupt her bolts (Mind Freeze);
Gunship - just have fun, IMHO it's the must entertaining, from a pure fun standpoint, fight in the game; though the horde captain is a bit bugged, if you taunt him too early on the jump he runs back then goes at your melee on the mage.
Surfang, don't AoE taunt (no DnD, no HB, and if adds are up no Heart Strike) you don't want the Blood Beasts to stay on stage, the key is range getting the adds off the stage and burning them fast; you need to be quick on the taunts when the OT gets the Rune of Blood on them. The fights a pain you don't need to help him heal himself.
If you get beyond this in a PuG you've done great. I've done Rottface and Festergut (only beaten Festergut on my hunter); so others will need to jump in.