Simple and easy the grasp, I can see the potential with more actions available (or more people tied together!). Nice spin on the theme.
(Don't read this part unless you've given it some plays). There's a broken strategy in continuing to heal-swap on the first guy, effectively giving the warrior unlimited hp if you have the patience. Let the warrior take some hits til the mage has prayed to 20 attack. That's easily fixed with a turn limit or slowly ramping attack.