I'm saying that I am using Prime Kurama... also... everyone knows that Prime Kurama is stronger than War kurama... however, that doesn't result in him being in a higher tier.
War Kurama output 2.35 GT of energy with his Bijuu Dama -- Small Island (-)
If we doubled that (Which it honestly doesn't work entirely that way unless it has been stated otherwise), it would result in 4.7 GT of energy, which is Island level (-), but barely. Naruto's chakra was also added into the mix and I am speculating that the Yang half of Kurama became somewhat superior to his Yin half due to his time with Naruto while the Yin half was pretty much in the stomach of a demon since Naruto was born.
It is safe to assume that Kurama in prime is Small Island +.
You were initially suggesting that Madara was using Continential Kurama: "
It would make Madara 7-A, but Kyuubi would still be what? High 6A, if iirc."
Hashirama with True Thousand Hands = at least Small Island+ for matching Kurama clad in susanoo
Madara is listed as Mountain... making him the weakest in the entire group.
Doflamingo is scaled to be at least Small Island+, probably Island (-) due to outclassing base Luffy and tanking Gear 4th hits while his organs were recently blown up.
Base Luffy is Small Island due to tanking Fujitora's ferocious tiger (Low end being Large Mountain, High end being Island (-)) without any visible damage. He would likely have resulted in being Island (-) if his rubbery body was not capable of mitigating a lot of blunt force, but considering that he was already injured, took the attack point blank, and came out with little more than a scratch, he is easily Small Island in base:
http://www.narutoforums.com/xfa-blog-entry/one-piece-calc-25-ferocious-tiger.26604/
Gear 4th Luffy is likely Island (-) due to overpowering Doflamingo (and due to Doflamingo's statement that Luffy's attack power multiplied: http://www.***********.net/one-piece/784/13 (a lot of translations suggest that his power tripled according to Doflamingo, so I believe it is safe to assume Island Gear 4th)
There is also the matter of speed: Luffy and Doflamingo being above Mach 634+ combat speed while Hashirama/Kurama/Madara are Mach 230+
Due to Luffy's blunt force mitigation, A lot of Hashirama's attacks would lose a lot of force behind their attacks. Kurama and Madara would however be able to harm him since both specialize in piercing/slashing attacks.
Doflamingo can apply low level Regenerationn on himself since he managed to repair the damage he received from having his insides blown up by Law's Gamma knife after some time and his Devil Fruit ability is specialized for trapping large opponents. I don't see Kurama being able to attack freely so long as Doflamingo is throwing Spider Threads everywhere: http://www.***********.net/one-piece/769/3, http://www.***********.net/one-piece/780/11, http://www.***********.net/one-piece/790/14
Hashirama has been stated to be capable of impressive healing capabilities similar to Tsunade's 100-healing technique, but I don't see him being able to win since I find Madara being killed by Doflamingo or Luffy to be relatively high and Kurama's reaction afterwards being controversal (he could defect, leave, or attack all present).
Given that Hashirama's body only has Town level durability, I see him being beaten pretty easily once he is melee range of Doflamingo or Luffy.
I'd find this fight to be much closer, but given Madara and Hashirama's normal durability, once their defenses are compromised, they are finished with an "Athlito" or "Eagle Bazooka" to the chest.
Of course Izanagi is a factor, but Luffy would be able to react almost immediately due to his adept level of pre-cognition. Doflamingo may not be able to react, but even if he takes damage, has shown being able to repair his body from injuries that would normally kill a mortal body instantly.