Summon cost is right imo, since the efford to be a summoner have to be like that.
BUT
still life tree is not appealing enough,
mana cost are too high there, and for example 20% heal ally is a strange way to heal, i mean: a knight receive 1000+ heal while a mage or a archer receive 600-700 heal, knight being able to receive more damage with all his protections should receive less than a defenseless mage that need more help to stay alive. That spell should be adjusted according to the class you healing, for example for knight is right 20% for mages and archer could be 25%.
Also the new spell mass heal should have less cd to be attractive 240 sec for 500/650 hp is not worth 5 points. I could understand more 180 sec.