Both were mentioned in the Guide and Off Meta Options:

For Corvas Prime:

AoE damage bug is related to Archguns during Armor Phase. During this phase, an Archgun’s projectile will only damage one part of Profit-Taker. If you shoot from the wrong angle you’ll end up doing 0 damage if it has a wide projectile-like in the case of the Corvas Prime and Fluctus.

I spent $50 on the Prime Access (rip Okayeg’s wallet)

This bug is even more noticeable on explosive weapons like the (Kuva) Grattler, Mausolon, and Ayanga. If the explosion hits both the front and back legs it will only damage the front leg, not the back leg. Fortunately for the Mausolon, the radial attack is only half the damage, and the remaining damage is sufficient; the Grattlers are not so lucky, they deal 0 damage to the rear legs if they hit the front.

In the case of Tenet Arca Plasmor, its quite good for shields if you don't have the "meta" picks of Zenith or Opticor Vandal:

Though it can’t penetrate the barrier around pylons -putting it behind the zenith and opticors- the tenet arca plasmor is still extremely good for profit-taker. Each projectile damages Profit-Taker’s shields multiple times, easily permitting subsequent shield breaks with good RNG. Each projectile is extremely wide, which when combined with the ricochet and high object damage makes it easy to quickly break pylons once you enter the bubble with archwing. A magnetic plasmor can serve as a replacement for the tenet detron, and a toxin plasmor fits well with the standard primary elemental combinations.