You might get more bang for your time by doing stockades until 25. I've noticed and some others have noticed as well that you get more XP per hour in there until your about 25. I personally did stockades, then SM:Lib (just run to the end, grab the boss, run back to the front with the boss in tow, repeat) then SM:Cath.

Once your 40 you can get your guys into BRD too. The Lycern (sp?) is awesome although VERY boring - and bring lots of extra shields. The mobs spawn faster than you can pull them, they all die within 2-3 consecrates, and net 15-20xp per kill, at 20-30 each on a continuous pull you can sit there and actually see your shaman's XP bar go up... Its really dull though and I ony lasted 1h doing it before wanting to rip my eyes out. (And I believe that pull is only really doable with a prot paladin - a mage might have too much downtime)