Even with max heal skill we're still looking at a 50 point loss of devotion.
Self-healing is a pinnacle ability for rangers (unless you're playing your character wrong) and this needs to be addressed.
Easiest solution: Give 1 point of possitive spell power for EACH AP spent in ANY ranger tree.
other solution: A low-hanging fruit line of cheap devotion enhancements. This does leave open the possibility of being "exploited" more on splash builds though.
Make it so.