All you have to do is get two Warriors with their special skills granted by the Dragon (inflicting deep wound and bleeding--sword) and three Rangers (one with Incendiary Arrows, one with Melandru's Arrows [or a second Incendiary to switch off with the first if the Warriors can cause bleeding], and one with Lacerate and Apply Poison).
Y'all enter the mission, Warriors take their special skills from the dragon, get to Shiro, lay down the Lacerate spirit, then continually inflict bleeding and poison and set Shiro on fire while the Warriors use their special skills (taking turns). When the special skills run out, kill a bonded, then repeat the process. What you'll get is major damage on Shiro with a constant degen of eight pips jumping to ten and back while the Warriors tank and deal additional damage.
And finally, "gg Shiro" in under 2:00 minutes. Yay for getting all three rewards on passing the mission!
