Nitpicky is good, it's the only way to learn! I;ll try to answer your points in turn...

Print or digital: We're aiming for print with a simultaneous digital release (we can dream, anyway). I've tried my best to match the font size of "real" books. Any bigger, and I feel the dialogue will be the focal point far more than the art. I wasn't sure where the line was to step over.

Panel 1 - Yes, I agree. I increased the font size for the exclamation just a little; I'm sure I could get away with enlarging it a bit more. I'm not sure about using an irregular bubble - wouldn't that stand out too much against the normal bubbles? Especially if they are used only once or twice throughout? I just wonder if that would jar too much?

Panel 2 - firstly, yes, once it's colored there'll be a spell effect cast from his hands; that should close up the gaps, hopefully (also, I'm told the artwork isn't finished, it was a character render with some background details still to be included - so that might also help). As for the bubble-to-text ratio, as /u/deviantbono says below, the spell was supposed to be cast as a whisper, hence the larger bubble. I didn't reduce the font size of the whisper because I thought going any smaller would make it illegible on digital screens. But I guess I could drop it down a point or half and still be readable. An irregular bubble here might work well, actually, given it's a spell (I even considered a "spell" font or "elven" font or something, but we wanted the word readable).

Panel 4 - I agree, and had intended to bridge the bubbles but felt I didn't want to encroach on the art too much. I could probably get away with separating them a bit more for sure.

Panels 5, 6, 7 - YES! Exactly this. Again, it was my attempt not to piss the artist off by covering up too much of his lines, but I didn't feel like I could reduce the overall font size any further. I think I'll enlarge those bubbles and see how much I end up covering, then head for the hills before sending back the draft ;).

Thanks for all your comments, they've really helped!