Moxsy is a good player and streamer but as with any Twitch/Youtube personality, you should take what people say with a grain of salt, regardless of their name, popularity or status within the community. No disrespect to him, but his Iron Bear build literally revolves around the exploit with Zheitsev’s Eruption in order to achieve what its video title claims it can do.
What happens if one day, Gearbox decide that’s too much and they patch out that exploit? Then his build becomes totally defunct and outdated. As always with Borderlands, to each their own, but if I’m going to make a build, I’d rather do it where it has longevity to it: not reliant on exploits and has scope to go further beyond if and when level upgrades come out.
Dual Vanquisher rockets with no augments is the highest burst-DPS - key word being ‘burst’ - for Iron Bear. The only downside to them is because they fire so many clusters of rockets so quickly, it drains through fuel rapidly and you spend quite a bit of time reloading. You can’t really control how many rockets you fire precisely because they fire in clusters.
In standard mobbing situations, you’ll likely fire more rockets than what’s needed, thus needlessly wasting fuel. That’s why some players prefer to run explosive Miniguns instead, or Railguns with Corrosive Sabot Round if we need to melt through some heavy armour. Both of those options are far more fuel-efficient and thus give you a lot more time inside Bear in conjunction with Deadlines.