What are you playing? c'mon, tell me punk!

[Garamonde]

The boss tends to attack more frequently if it is near to a Captain, so if you leave Brittany and Charlie somewhere out of reach, you shouldn't have too much trouble beating the boss by charging and whistling and just keeping Alph far enough away to avoid triggering an attack.

If you don't care about speed, you could just use all Rock Pikmin, which the Plasm Wraith cannot impale at all.

Yea I actually noticed those things. Currently I'm trying to get platinum rank on it and I just can't seem to figure out how the hell one is supposed to get it down to its second phase, let alone defeated, within 5 minutes.