MG combo or Fire Slash bug.

Hello.

I don't know if everyone are familliar with this - MG also have some sort of combo skill:

1. You must equip a weapon with skill (Lunge, Cyclon, Uppercut, etc.)
2. Hit a monster with Fire Slash
3. After hitting switch on weapon skill
4. Your MG will inflict 2 or more ( depend on attack speed) Fire Slashes really fast with no AG cost.

Lots of players think that it's a "Fire Slash bug". But I don't think so. I also checked the Global server. And it was working. But on the new season ex:702 this combo is removed. I read players complain about it in Global forums : "Bring back Fire Slash combo" , "...leveling a SMG is now so hard..." , etc.

So I have some questions I want to discuss with you:
1. If it's a bug but not combo why gamemakers will create a sword that can only be used by MG and this sword will be with DK weapon skill not Power Slash ? - http://lotusguides.net/images/guides/swords/thunder.jpg

2. Can I use this combo for leveling and PVP ?