I'm still mystified as to why they haven't improved healing and revive XP by now. I'm especially concerned that you get a paltry 3/6 for base healing/critical healing which is just too low for how useful and important it is. Revive helpers should get an XP reward too to encourage such behavior as well. BfN has a greater focus on teamwork than ever before and yet so many actions that directly help your team are not rewarding enough. Keeping people healthy and getting downed teammates up near/on objectives should be appropriately rewarded and right now it isn't.
I would make healing 10/20 for healing/critical healing and don't think it's too much as A) critical healing is only on allies that are close to being vanquished so it's a limited XP event, and B) we need to encourage more healers and giving them an incentive to do so would make them more appealing so they'd be played more.
I've pointed this out before but as a prime example of what I mean, Sunday I had a PvP challenge to get 2k damage in a match and got it on Preserve Pastures as Electric Slide so switched to Scientist as we had none on the team. I did this for the last point with the Gargantuars and was healing them and my team like crazy as my Scientist build is all about heals, so much so that I had over 2k healing for just that last point, had number 1 healing on the team (A Sunflower had more so got the podium), but the healing portion of my XP was far less than my damage/attack portion so I was in the middle of the pack. As the team's only healer and still getting that much, it should have rewarded more generously as no one else had more than a pittance from healing zombies summoned.
This is still my number one issue with XP right now. Healing and reviving for any mode should be encouraged and the best way to do that is with greater rewards for doing so.
Edit: and yes, if they nerf Sunflower's healing they have to give her some other buff to compensate.