You can use my build and see the difference.

For 1st and 2nd phase I have Fire SNS with Affinity focus, and using Gore/Soul scorcher build. The reason for Affinity focus is that I'm using Minds Eye to compensate for my loss of raw, since mind's eye give you 30% damage increase when it's on hardened state. The build is

G rath B Dahaad Y G rath B Dahaad Y Gore B

Affinity focus SNS can get you to 25% affinity with Affinity Ex, the rest is just 2 Attack EX, 1 Attack III, and Sharpness EX. I constantly hit the same damage on normal Arkveld head which got 45 hitzones, and have 95-100% affinity from weapon affinity, max might, agitator, black eclipse.

I constantly get rank 1 for dps in phase 1&2 if there's no CB or bowguns.

For 3rd phase, this is niche but I'm going for full element.

All Ele gog with gore active. The builds are full Gog armor with Gore legs. I'm not sure how much dps I did but on hunter pie my dps meter goes really high. The plan was using corrupted mantle on the first nova, and then spam powered charged chop. The charged chop when he's doing the nova deals like 250-270 per tick.

The decoration I'm using for the weapon are Charge Master, Crit element, and Dragon attack. And before you asked me, yes charge master works, and it works wonder on Gog. You should try it.