Ah if you pay attention to the Mighty Gunvolt Burst Website (http://mightygunvolt.com/en/MGB/), it actually gives out some pretty important patch notes such as for various effects and actions affected by the current burst combo like Collapse Ray and Luxcalibur, they will now change according to the following:

Level (LV): Burst Combo

LV.1: 0

LV.2: 1-4

LV.3: 5-9

LV.4: 10-19

LV.5: 20-29

LV.6: 30 or more

So for bosses like Battalion and Pyrogen, if you’re trying to get a Collapse Ray quick kill with 1.5x attack power; you will definitely NEED a LV.6. You could get away with a LV.5 or 4 with 2.0x attack power and a LV.3 or less with 3.0x. Plus elemental weaknesses make a difference too.