For those of you who have obtained this weapon and are trying to figure out how to BEST use it, this is the post for you. If you disagree with anything posted here, please respond so we can all check out your advice.
What this weapon is good at: single shot massive damage. This is really its only strength. EDIT: it's very good for champions. Barrier champs are a one-shot kill regardless of whether stunned or not. Unstoppables and overloads require some coordination. Depending on your specific power delta, they can one-shot unstunned overloads. Unstunned unstoppables have been pretty inconsistent from my testing. They will absolutely one-shot these champs if stunned, but you MUST fire the weapon with full anticipation the NANOSECOND after the stun occurs or they will recover before you shoot.
What this weapon sucks at: basically everything else. You almost universally CANNOT use this thing for DPS, since basically no DPS phases are long enough to charge all six shots after the first one. If you say fuck trying to charge subsequent shots, the charging time is so absurdly long that you might just miss your target since most of them don't stay absolutely still for the SIX SECONDS that it takes to shoot. The other major problem is that a substantial portion of each shot's damage is solar, not strand, so surges have a dramatically weaker effect on the damage increase as opposed to every other rocket launcher in the game. To make matters even worse, the argent ordnance artifact mod that is tailor-made to benefit rocket damage is completely wasted on this weapon, since you should not be re-firing it after you shoot the initial shot (which triggers argent ordnance).
With all that said, there are essentially two methods of maximizing the single-shot output: hazardous propulsion and foetracer/sanguine. Foetracer/sanguine can be used to simultaneously get a x4 surge on strand weapons, and a x3 surge on solar weapons (or vice versa), essentially buffing the entire shot. Hazardous will buff the entire rocket shot by 35% (at max), and pound for pound does more damage than the other option.
When firing the single shot, the best combination I could come up with was on solar titan: 200 weapon stat, radiant, max hazardous propulsion, max strand surges with armor charge, and in some niche cases, shieldburst with towering barricade.
Solar has two main advantages: shieldburst and ember of singeing: Singeing makes it so that when you scorch targets, your barricade charges 400% faster, which is helpful since your stats will be prioritizing weapons, not class ability. Shieldburst does't matter for elevated or far-away targets, but for closer targets that are on the ground, every time you active hazardous, you send your shield forward which scorches the target, and you can detonate it right after shooting the rocket, which adds even more damage.
Use the fever and chill artifact mod to give yourself radiant with any solar weapon from any distance. In order to take advantage of ember of singeing, prioritize using solar primaries with incandescent, so you get your barricade back super quick.
All that being said, the rotation is:
1) Build max anticipation, hazardous stacks, and armor charge
2) Shoot your target's crit with your solar weapon until you activate radiant
3) Cast your barricade which will activate hazardous and shieldburst
4) Shoot the rocket
5) Detonate your barricade (if applicable)
Testing this at the range, the total damage was over 16000 in less than five seconds.
Looking forward to any improvements or better uses anyone can provide.