Of course these are just my suggestions, I do t necessarily care if Bethesda changes these verbatim but these perks and the endurance tree in general needs help.
End 2 - Lead Belly. Lots of people criticize this perk in general since there are so many consumables and radiation is easy to deal with. I still like the idea of this perk even if just from a role playing stand point. Currently though it's too much to dump 3 levels into it for a bit of convenience when roaming.
Change: it needs to have only ONE rank, which removes radiation from consumables and water.
End 6 Rad resistance. Easily the worst perk in the game. Even with a staggering three ranks of this perk you still only get 60, yes 60 resistance to Radiation, a single rad-X pill gives you 100. There are many suits that offer considerable rad resistance. And once again, radiation is still pretty easy to fix. There's no reason to put one, much less three, level points into this perk.
Change: rank 1 adds 50 rad resistance. Rank 2 adds 75 rad resistance and rank 3 adds 125 rad resistance. This would give you a respectable 250 total resistance.
End 9 Ghoulish. Sounds interesting but it's pretty lackluster perk - especially for being rank 9 in a fairly lackluster tree anyways. This perk feels rushed and poorly thought out. Also, one of the best parts of this perk rank 3 doesn't become available till pretty high level. One of the biggest problems with this perks is the negative synergy with the two previously mentioned perks as well as Aquaboy(since they all reduce or eliminate rad intake).
Change: Rank 1 small chance for feral ghouls to become friendly, radiation of 1-3 is CONVERTED into 1 health. Any existing radiation is removed at rate of 1. Also, this only applies if the radiation is from a continuous source.
Rank 2: There is a good chance Ferals will become friendly. Radiation of 4-6 is converted into 3 health and any existing radiation is removed at Rate of 3.
Rank 3. A leathal hit has a 50%chance to restore you to half health and emit an intense wave of radiation.
So basically if you are rank 2 ghoulish you get 3 health regen if you are standing in atleast 4 rads. Up to 6 rads you do not take radiation damage and are healed by it. You will also still be removing rads at a rate of three. Above that though, you are still getting healed but also taking on radiation.
So basically taking small doses of radiation/standing on the edge of irradiated areas are very beneficial but radiation will start adding up once you get to much of it at once. Also, since ghoulish would only work from Constant sources it would still allow lead belly to be useful and since you start gaining rads at higer concentrations it would synergize with Aquaboy since irradiated water is usually at 10+.