I tested it heals in between waves in the spire. Personally, I think 5% is great regarding that it heals all the troops not just one. Obviously, it's not as overpowered like fire phoenix, but still it's useful and reasonable.
On live, I have 450 lvl wonders, several premium extensions, and I was struggling on lvl 3 spire and after 17th tourney to even win fights, while before the big algorithm change I was going until 39th tourney with half the AWs. So I think this still gives some advantage and saves considerable amount of troops. When I'm fighting with 30k squad size. It's something if I get back 5x5% per wave.
Not to mention, as far as I see they put a lot of options to get EC. So making it even possible to push this higher. I have 2 lvl 7 Ashen on live. Waiting to get some more evos in spire on day.
And imagine with polar bear, timewarp. You could do all the tourney, spire and scouted meetings in a day. I'm really hype. There are so many options.