Wouldn't your solution then, be for the healers NOT to heal you then if you're topping yourself off? If they're spam healing you when you're capable of topping yourself during that particular time, then yes that's mana wasted since they can hold off during that time.

Unfortunately, I'm not at that level yet, so I don't know how high level wars operate, but as a general rule, I usually avoid over healing as much as possible... so unless you're getting popped for 80% of your health in 1-2 hits, I'm adjusting to the pace your HP fluctuates. Having no experience with IB, I have no idea how much a war heals themselves during that interval, but I'm assuming it's enough that I could hold back and wait til the buff is nearly out before heading again.