* Bug report
Thanks for the feedback and reporting the bug! We'll look into it and try to reproduce it.
I think there are some gameplay issues.
Thanks for taking the time to write such detailed feedback!
I'll try to respond to each of the issues you brought up as best as I can.
The game plays a very differently between the normal and hard modes. It's actually recommended that you started off on normal first before playing hard (although we didn't really say anything about that...)
1) We initially had a tutorial to teach the player to use the left-click button to walk. But most of the playtesters had mentioned that they felt it was redundant, so we put it in the how-to-play screen and took it out from the in-game tutorial.
We've seen some players play the way you did, barely using the left-click the entire game, but the majority of them used it quite frequently.
We've had more complicated controls using the keyboard, but we found that it was generally very confusing for players on their first time. We wanted to cater to a wider audience with simpler controls and ever since we've changed it to be in it's current state, the feedback has been mostly positive (so we kept it!).
2) The healing mechanics don't apply to hard mode as much because, as you discovered, you pretty much die in a single hit if you're not careful. It's noticeable on Normal, I swear!

3) The intention behind the no-frontal-damage using chains was deliberate because we didn't want players to lay out their chains only to have their asses kicked when the enemy happens to turn around while they're executing their plan. We didn't want the first level to be excruciatingly hard because it was meant to teach people how to play the game (we've had several people rage quit because the game was a lot more difficult at one point).
4) The introduction to the Clerics (staff guys) was actually intended to be a surprise. We had wanted to put a tutorial to explain what they did at first but we playtested it before we had the time to do so and players seemed to love being surprised that they could target you on a torch. Their bullets kill you in one shot on hard so if you were right when you mentioned that you crossed it while chaining.
5) Actually, the boss fires the blue strikes the torches in a planned sequence (depending on which sequence she chose). It may seem a bit random but there is a pattern to each batch of strikes

Even though you've been given 10 chains, it usually works badly on the hard difficulty when you just place all your chains at one go, because each shot will insta-kill you. All I can recommend is that you try the game on normal again to see the difference!
Bug) We actually timed that sequence to last exactly long enough to make sure you'll never get hit or die from those stray shots

If you die from it though, let me know! I'll have to fix it, heh.
We did quite a lot of playtesting during the course of the game's development and we were faced with the challenge of making the game simpler to cater to a wide audience while keeping it fun and challenging even for the veteran gamer. I hope the explanations I've given for the design decisions we made made sense! I'd recommend just trying the game on Normal for a bit to see how it differs

Again, we really appreciate the feedback and I'd like to hear from you again about the differences!