So the 4-piece bonus for Typhon's Veil is geared specifically for defense. It seems to have no advantages, only negatives, if you're not having any issues with squishiness:
"Damage taken is reduced by 8% for each Hydra head alive, as long as there is one available. Each time you take damage, a Hydra head dies, but no more than once every 2 seconds (4 pieces)"
I found the shoulders and had a RORG, so I tried out the 4-piece bonus. It was depressing. Basically, every time you take damage, one of your Hydra heads dies. I have no idea why this is seen as a good thing. The first part of it, "Damage taken is reduced by 8% for each Hydra head alive", sounds great, except that if you do manage to take damage, you start losing heads, so your damage reduction is also reduced (since it's tied to the number of heads, which keeps going down), and pretty soon you die unless you keep spamming Hydras to keep the number of heads up.
So I switched the shoulders back out, as I am not currently having any issues with defense. Swapping out the RORG was not an option as it's in the Cube and I have Sage's and Captain Crimson's bonuses going on for now.
The 6-piece bonus "Hydras deal 1300% increased damage for each Hydra head alive (6 pieces)" massively cranks the damage, yay, but as soon as the action starts, heads start dying every 2 seconds, so when you need it most, your damage reduction goes down and your damage dealing also goes down. Again, I'm not sure why that's supposed to be a good thing. Presumably it's not as bad as it sounds on paper.
Been gambling gloves non-stop trying to get a fourth piece of the set, no luck yet. I still need to try out the 6-piece bonus to see how it all works, but on paper it seems kinda wonky.