If it's any consolation, Ixy, I don't think that power use was a waste.  A five square area should cover Lulu and Damian, both of whom have some use for 8 temp HP.  It would have been nice to cover a larger portion of the party (It's actually a fairly nice quantity of HP you're handing out if you hit enough PCs), so I think you're absolutely correct that the tactical wisdom gained is worth the use of the power.  This is not the last fight we'll ever get in.