I really don't see a problem with it.
Look at Polymorph, and compare it to this. You can get Much more powerful strenght with Polymorph. Not to mention a lot more different effects.
All this does is raise your strenght to the maximum of 18 (Your 20 Str Orc Cleric has no use for the strenght increase), gives a simple upping of BAB, and some HP's. So it's just an Endurance, Bull's strenght (Strenght pending) and an easier chance of hitting.
Compared to Restoration, which fixes ALL level losses, ALL ability damage, or Poison, which can cap 20 con damage, I think it's a fair spell.