I don't have a problem with the increased healing capacity, as it is, in fact, a trap for the party!
If you let the cleric increase the amount of hp each surge restores after a short rest, you reduce the amount of healing surges required to heal back up to full hit points. As a result, the party will be able to go through more encounters before they run out of surges. However, this means they have to spread out the use of their daily abilities over more encounters, and the party's overall power goes down.
(I base this on the observation that the party IMC mostly takes an extended rest when they are running out of healing surges, and only rarely when they run out of daily powers.)
So, let them "exploit" the system, I say. It really doesn't increase their power.
- Enaloindir