So I got this sword for 2 reasons.
1. It looks cool
2. I was interested in the energy bolt per swing mechanic
Now i found this sword quite a mixed bag really being very good in some situations, good as just a general sword and terrible in 1 situation that should be avoided at all costs. A short explanation first though. the sword performs a 6 hit combo, 3 swings, 3 disks. The swings are very much like a calibur or brandish however they move you forward a much further distance. On each swing a energy disk (small bullet basically) is fired a few tiles in front of the user, this can trigger the block and dodge reaction from enemies like: Wolvers, Gremlins, Devilites and Mecha-knights. The Charge attack is a powerful forward slash and a large energy disk that can travel through numerous enemies.
Pros
Good VS Beasts
Good VS Deviltes
Good VS Greavers
Charge attack is good VS Crowds
Destroys minerals fast (not really a pro but worth noting)
Can trigger far switches without switching to a gun
Cons
No 5* variant so not as effective during the end of tier 3
Can accidentally trigger switches you didn't want to trigger
Can trigger explosive blocks near you
And here is the biggest con of all. The Winmillion is absolutely dreadful against Mecha-knights and can easily get you killed in a group of them. Heres why, Mecha-knights have a block ability which is triggered by the Winmillion's energy bolts. You start swinging at it and the knight will block all your attacks, when you finish the combo you are vulnerable for a split second, it this second the mechaknight will attack causing substantial damage, in group of 3-4 of them this can easily kill you. I decided to further test this in the arena level robo rampage. At the end of the final room the area fills with Mecha-knights. I died. A lot. I attacked they blocked and attacked me back then i died.
TL;DR Don't use the Winmillion against Mecha-knights they will destroy you.
All in all i think it is a very good sword so its a shame there isnt a 5* variant to finish off the line but its still an equally viable weapon at 4* just as long as you have a weapon with you that can deal with Mecha-knights.
Hrrrrmm... Do you use Auto-Target? In my experience, you can't really hit Devilites well without it. I know how to control Devilite dodge movement with bullets now, but seeing as you say that Winmillion is dreadful against Mecha Knights, I doubt you have the experience to know what I'm talking about. Winmillion isn't terrible against Mecha Knights, it's quite doable to fight crowd of Mecha Knights without a mender bothering you.
I suggest stop using the full attack combo on everything (which it seems that you are doing from your post).