Re: the randomisation - yeah, makes sense when you put it that way, the lack of variety makes what could be a distinct mechanic become simply annoying. In that case, I haven't really paid attention, but does the game indicate the characters rarity at the moment? Because either I haven't noticed, or it didn't. Either way, maybe add rarity colors to character names and whatnot, to more clearly delineate between rarities? Provided it's possible, of course.
Re: side buttons - I was indeed wondering whether it was some sort of targeting priority selection, glad to know I wasn't too far off the mark. Still, it's not immediately obvious what they do, so the point still stands that the game doesn't explain some details well.
Re: leveling - I swear, it really does feel like between a fresh game and getting her to stage 2, Lyra is still the same, with an initial 10 dmg that increases by one every in-game lvl up, instead of supposedly starting at 14 dmg in the latter case, as the upgrade screen would suggest. Also the experience is transfered between towers ont he same spot? Weird, I thought it completely resets, and the newly placed tower basically starts from scratch.