Clefthoof is underrated as potential tanking pieces well into tier content so I wouldn't worry too much about it - I tanked well into tier 5 before getting rid of both the leggings and chest (the chest is particularly tough to replace if your guild hates doing Mag, as mine did). Apart from that, Pzychotix is mostly correct about the pieces you can substitute (albeit there's no tanking ring off Maiden, it's the Shermanar ring off Aran - there IS the Barbed Choker of Discipline off Maiden but it's inferior to either of the badge neckpieces for druids).

At the moment I'm mostly staying defense-capped through a combination of the def/dodge helm enchant, substitutions of the S2 shoulders in place of Tier 5 (both with def/dodge enchant), Vindicator's Dragonhide bracers, two rings with defense, and the badge cloak with defense (albeit inferior defense to tanking cloak off Illhoof). You can also slap a defense enchant on the badge bracers and/or the new 15 defense to chest enchant coming in 2.4. I also use the S3 chest for tanking which helps a lot (I'd much rather be using it for DPS but our warriors were horribly undergeared in Tier 5 content so we passed them the tier chestpieces).

Make no mistake, it IS hard to stay capped the further you get into tier content, but it is possible if you mix and match a bit. For magic-based fights PvP gear is typically better; for heavily melee-based damage fights, stack as much armor/agi as you possibly can while still staying capped.