Why couldn't you see others going through something similar when facing hancock? Quite frankly, characters like aokiji or kizaru would seem all the more vulnerable to her ability due to their personalities..... I don't think what the admirals did to protect the island from the quake would work against hancock's ability, its two completely different things. Sentomaru also protected himself from luffy but I doubt the same kind of protection would work against hancocks ability....
The Admirals negated an attack made by a Devil Fruit power (and Sentomaru negated Luffy's rubber defense and Gomu attack) with (what I assume was) Haki. Following that line of thought, Hancock's Mero Mero Mellow technique should be no different since it is, essentially, a Devil Fruit attack. That is, however, only speculation.
Even if I'm wrong, and you can't use Haki to defend against Hancock's Mero Mero techniques, I'd think that the Admirals have sufficient self-control to avoid being turned into stone without resorting to stab themselves (whereas Momonga required present pain to focus upon to escape the love technique (hence the self inflicted wound)).
The adrenaline hormones allow luffy to ignore fatigue for 24 hours as said by iva. In that sense, its effect was about as good as hours before.
I was under the impression that the adrenaline hormones supplied you with a burst of adrenaline (hence relieved you of tension from any pain and fatigue (as adrenaline does)). So as the adrenaline gradually runs out, Luffy would gradually begin to feel all the fatigue and pain he had stockpiled (and the adrenaline were obviously running out by the time he got the "fodder treatment" by Momonga and the unnamed VA).
And the 24 hours thing was the after effect that Iva-chan warned Luffy about, that it'd be a price to pay later for the extra energy.
Luffy not even being able to activate gear two against the VA does not help his cause. IMHO any of the admirals at this point would give luffy (and his entire crew) the fodder treatment. Anything less than that and the third greatest marine asset would be seriously worthless considering what we have seen.
Any of the three Admirals would indeed have little to no trouble with the entire Straw Hat crew, as they can't even harm them so I assume you meant the VA's. And though I certainly agree that there should be a few among them (barring Garp) strong enough for that, I don't think it's implied that Momonga would be one of them...
If every single one of the VA's is strong enough to solo the Straw Hats without a scratch to tell the tale, it'd make the Shichibukai (at least Crocodile (who fought skirmishes with Doflamingo and Mihawk) and Moria (though the Gorousei seemingly agrees with that thought ^) absolutly redundant.