Originally Posted by
econ21
IIRC, the tank stats on heirlooms are mainly avoidance, while the dps stat is mainly crit. I have both but I'd say it's a wash - and tbh, probably prefer crit (damage is low while levelling and I like doing more dps than the rest of the party combined).
Ideally it is worth getting the BOA shield and a one hand if you don't have them. But leveling is so fast, it may not be time efficient. (I find converting honour to JPs can be a way of getting JPs fast).
One small tip: take off the L1-85 heirlooms at L80 as the scaling is horrible at that level alone. You can put them back on at 81. Also Cata dungeons have an ilevel requirement and heirlooms count as L1 or some such, so keep non-heirloom versions of slots in your bag so you can queue.
And keep an eye out for MoP or Cata gear with low level requirements - some MoP blues can be insanely OP at lower levels.