Personally I think that the real danger of a dragon are not its physical attack capabilities but rather its the spell the beast can cast. A great fire drake in RM has an OB of 150 for its claws and a DB of 75. This, while coupled with AT 20, 600 hits, three attacks per round and the beast being a super-large creature, is quite impressive, but we had some fighter characters who had such OB and higher DB values even at 10th level. Therefore a group of 3-5 such fighters could deal with such a beast. The problem for us always was that, for a 60th level drake, it was very easy to simply cast a Word of Sleep, Lord Sleep, Suggestion, Master of Kind or the like and put the characters to sleep or dominate them. Unless your group finds a means to protect against such spells it is IMO madness to even try to battle such a beast.