Originally Posted by ngtrungkhanh

Try hard to clear ?-4.
The bloom drop rate is almost 100%
I played ?-3 five times and only got one bloom

Originally Posted by thewind32

Indeed, don't bother wasting time and stamina on ?-3. I've cleared ?-4 twice so far and gotten the drop both times. You do not need to clear everything on the ?-4 map, just the final boss to reach the chest. Look for a stronger helper squad.
Otherwise, you still have time to farm normal maps and strengthen your teams.

Just as I feared... I'm still a bit far away from clearing it even with my strongest friend as a helper (53k pwr) as I started playing around 11 days ago. I managed to get one skill bloom yesterday so here's me hoping I can hit a lucky streak and get the skill up to at least 4/5.