It`s true - only 0.3% of our players buy crowns, and we look at it more of a way for players to donate to our company, rather than us greedily milking players, and as you have guess - we are not making much on this at all. Besies - we treat these funds - as players "investing" into new content, and. So for example whatever funds we got from Crown sales in April/May went into paying for the 4 (with 2 more to come) new units we added in July. And with current income we received for Crown sales in June/July we plan to add several new units later this summer.
To some extent I agree with 60% cap and self-healing decrease. As you could see we are constantly working on the balance - with every patch bringing new changes, so with time we`ll find the right values be it 60% or 70% or 80% for resistance.
Sorry to hear about your bad experience. I`ll raise this with our balancing scripter Vicious and see if maybe it`s time to lower resistance/self-heal rates.
Keep in mind though - if you would have had stone walls - these heroes would be unable to breach your town walls. Also the max limit of units you could have had in your town was 90. And as another player suggested - it`s really easy to deal with these heroes by focusing all your units on one hero.