If I'm reading Shades (and Greater Shadow Conjuration) correctly, they both increase the damage dealt by the summoned creatures (to 80% and 60%, respectively), but do not increase the hit points of the creatures summoned.
So, for example, using Shades to summon an elder earth elemental with... 34 hit points seems like an utter waste of a 9th-level spell to me.
Am I missing something, or is using Shades to summon a melee-type creature just really silly?
Jade Regent Spoiler:
The trap that summons 1d4+1 fiendish dire tigers on the party is sure to do quite a bit of damage to the party... until a single Fireball kills all the dire tigers at their whopping 21 hit points each.