Thank you for answers!
1. But Orodruin was hardly "more powerful being" than Sauron, and its flame was hardly hotter than that of Ancalagon... yet it managed to melt One Ring just because "it was forged there"
And were Nazgūl really less powerful than the Istari? If so, it is strange that Gandalph, for example, never really attempted to destroy them... You may say that he was forbidden to use greatest part of his power - yet he used it against Balrog...
2. Even is airship was much smaller, it is hard to believe that it could withstand massive amount of flame (and Ancalagon was thre greates living flamethrower ever, no doubt) during their loong battle, yet alone penetrate his armour (remember how tough was Glaurung scale). Well... I guess it is more of legend than militray chronicle after all)
4. But why he concentrated so hard on building orcish armies (orcs, even though they were created specifically for war, were bad warriors - took horrible casualties even when thyy did manage to beat elves with the help of Balrogs/etc.)? He did not seem to pay much attention to quality (did trolls ever do something impressive? No other formidable monsters were created...except Balrogs which could not be "mass produced" though) as well, until it was too late. Hmm.
P.S. Is it mentioned anywhere precisely whether Valar themselves fought in War of Wrath or not?