I have an issue where the bot doesn't fully make use of Heroism/Bloodlust.

The gcd shortens for me during this period, but it still takes one full second before the bot reacts to this.

Is it possible to shorten the cast time or make it queue the next spell faster?

Look into "is spell usable" instead of adding a cooldown, this way it just checks if the spell is ready to be cast.

and try putting a faster frames per secound as well if your computer can run it