To add to my earlier comments: The balance on multiple attacks feels like it might be off a bit. It rarely if ever feels worthwhile getting a 4-damage attack when you can get a 3-damage multi-attack for only 8 gems.
I suspect that solo attacks should have a significantly higher cap than multi-attack (6 damage?) and/or multi-attack should be significantly more expensive.
(I suspect it's the latter, since it's essentially never worth getting lower damage multi-attack either at the current cost structure).