Having non-regenerating health, but giving player access to simple healing spell is wrong on 3 accounts:
1) It kills the whole mechanic, cause you can just wait the cooldowns and spam healing after combat, geting everyone back to full without any cost or effort.
2) Makes a mage with healing spell an optimal choice for any party and therefore a must-have, unless you want to purposefully nerf yourself. Something like that is always a bad design decision.
3) Encourages player to wait after each encounter to heal whole party with heal spell, instead of "wasting" potions - which would make another bad design decision.
Therefore, access to unlimited healing is pointless if you introduce non-regenerating health mechanic.
On the other hand, we probably have some kind of group heal as a focus ability (it's in the tree description, and nobody said it was removed), which makes such a restricted healing a much more powerful and worthy of speccing in a tree ability. A mage that can bring full party to health mid-encounter is a really valuable asset - but because it's a limited ability it' not a must have.