G'day, Jeff!
It's actually an EL 7 Red Dragon.
A party of four sixth-level character should be able to beat the Red Dragon and the Hydra... because they are likely to be the only encounters for that particular day of adventuring. Rest and recuperation are key to a lot of these modules, as you proved when you rested before going after the Kuo-toan priests.
Mind you, the Cryohydra is tough...
The Erinyes, however, is almost too much. Looking at the actual module, I don't think it's too much, though, for a normal party. Your party is extremely sub-optimal at the moment: you're at the worst levels for a mystic theurge, and you're the only spellcaster. A normal party will have a 6th or 7th level Cleric and a Wizard for these encounters. Tough? Absolutely.
The do think that a really paranoid and clever party shouldn't need to face the Erinyes. The really nasty thing about the set up is that it occurs just after you've let your guard down, having dealt with the priests.
Cheers!
For that matter, how was a 6th-level group supposed to beat an EL 9 red dragon? And an EL 8 7-headed, 21d6-breathing hydra?
It's actually an EL 7 Red Dragon.
A party of four sixth-level character should be able to beat the Red Dragon and the Hydra... because they are likely to be the only encounters for that particular day of adventuring. Rest and recuperation are key to a lot of these modules, as you proved when you rested before going after the Kuo-toan priests.
Mind you, the Cryohydra is tough...
The Erinyes, however, is almost too much. Looking at the actual module, I don't think it's too much, though, for a normal party. Your party is extremely sub-optimal at the moment: you're at the worst levels for a mystic theurge, and you're the only spellcaster. A normal party will have a 6th or 7th level Cleric and a Wizard for these encounters. Tough? Absolutely.
The do think that a really paranoid and clever party shouldn't need to face the Erinyes. The really nasty thing about the set up is that it occurs just after you've let your guard down, having dealt with the priests.
Cheers!