I was searching for more in-depth info on how exactly it works and I see a lot of people saying it only works with the summoners minions. Is that accurate? I thought that it had an effect on regular towers too but I never looked at it too closely and I did notice that walls and the like need a lot more repairing even with a mage behind it than my ogres but I assumed that was just because the ogre killed stuff fast enough that the damage from attackers never outpaced the healing. Does anyone know exactly what it heals and what it doesn't? Also what stats have an effect on it?
If you believe that Abed is the true Messiah and you are 100% proud of it make this your signature. http://oi44.tinypic.com/lfdsi.jpg
I think the heal is fixed by percentage, so it's not affected by Tower Damage (but the fireball is) though both heal+fireball may be affected by Tower Radius and Tower Cast to a negligible degree.
If you're going to use walls (pretty useful in late survivals but I'd stick with minion walls in campaigns) I'd suggest a dedicated Tower HP EV. Super easy and cheap to build (Mine is 5k stats using all trans and my builders are only close to 4k) and can negate those instances of rage inducing ogre glitches.