Totally agree that the blue enemy should be more intuitively distinguishable. Actually, during the development time I even said something like "That looks more like a mana crystal/orb", but I started the project quite late and I sort of ran out of time.
Regarding the hitbox, initially, I was planning to make the regular attack's range upgradable just like the skill attack, but ended up scrapping the idea at the last minute. Hopefully, it didn't frustrate you too much ( T . T )