Rupert, my level 32, great-sword wielding warrior came up against Raghot yesterday, accompanied by his friend, the fragrant Aela (for Buck and Serethil, he has given her new armour and insists that she swims in the rivers regularly so that the odour of wet dog just adds a hint of mystique).

Yeah, that's a set-piece battle, so there is always an Elder among the four. Fortunately, you rarely get more than two at a time, and that's not all that common either.

IIRC, it's Elder, Frost, Fire, and Blood dragons.