After seeing your post, I tried it on ios last night (where it is free) for a while and enjoyed it and will likely play it some more.
The battles are not especially strategic as they play out on small fields, but it is TBS with cards, which I like. You only get 3 cards per hand per round, so that limits what you can do in a battle, but some cards create allies for you, and they each have their own movement and attack characteristics.
When you defeat enemies, they give you drops, which are health, equipment, cards for your deck, or d20s. Yes, you want to collect d20s, as certain things you try to do require you to roll over a 15 (for example), and the more d20s you put towards that roll, the higher your chances of getting a win. But once you use a die in a roll, it’s gone (they are expendables). This is an interesting and unique (to me) system, though you seem pretty limited in how you can acquire dice, and they seem kind of essential.
You level up as normal, and once you reach certain levels, you unlock more heroes to play. You can also buy hero packs to expand your options (this seems like it will be unnecessary for quite a while), which I’m ok with given that this is a free, well-made game (on ios). As advertised, there are no micro transactions or currencies or other nonsense that plague FTP.
There’s a chapter 1 tutorial too, so it immediately walks you through how things work very smoothly, which I always appreciate. The graphics are perfectly fine and by no means mind blowing in any way, but at least they’re not pixel-art, which I’m real tired of. There is no plot really to speak of, and levels are randomly generated. Several difficulty levels to chose from, and Normal seems perfectly challenging for me ATM.
In all, it does a solid job at what it sets out to do, and I’ve enjoyed it. I would not pay $30 for it in any reality. If the steam version includes the other heroes/expansions, I might pay $10.