@"Gandalf claims to be the most dangerous thing Gimli will ever meet unless... this cements the power hierarchy (as Gandalf sees it) as Sauron > Gandalf the White > everything else."
Heresay at best. Who knows whether Gandalf is right in this. On middle earth in the third age there is Sauron, Sauruman, possibly other Balrogs of Morgoth, Galadriel and Elrond (weilding rings of power), the Witch-King of Angmar (also weilding a ring if power), Isidulur's heir (who could potentially take the ones ring, and this would scare Sauron) - unknown dragons, whatever Tom Bombadill is, two missing Istari, Radaghast the Brown, and Shelob.
Arguably Galadriel is Gandalfs equal in many ways. Both have a ring of power, both saw the light of the trees, both have millenium of experience. Galadriel is a grandchild of both Noldor royalty and Telri royalty. Easily the most prominant elf in middle earth (and given the hierarchy Vala>Maia>Elf>Human, and the evidence that the greatest Elf of his time (Fingolfin) can best the greatest Vala (Morgoth) in single combat (he wounded Morgoth seven times, which would have been more useful if he hadn't been fighting an immortal god) there is every reason to believe tere is overlap, so the best elf could be better than the weakest of the Maia... Thus we do not have a strict heirarchy) could have out done the random Maia picked to go to middle earth - gandalf wasn't the first to be picked, right? He was sent as an after thought?