Having just DM'ed the original Temple of Elemental Evil I have to say that even with the new AI, the game is nowhere near as deadly as the original campaign that Gygax created. If you read the module, when the pcs clear the moathouse, it says that there will be a level 10 assassin sent after the party. Their rogue was level 5, but most of the party was 4th level, with the fighter mage level 3. I had to fudge the battle so they would not be killed.
Just becose it's said that the assassin is send to chase the party, this dont mean that the assassin will arive on then in the moment that the band put the first foot outside the moathouse. There will be some time between the Temple discovers that Lareth is dead, and who kill him, and then decide to send an assassin to kill the group. And, as General Ghoul sais, there are, actually, a level 10 assassin that will chase the party, if the group let a trackable path behind they.
having trouble with the hommlet quests any suggestions to them? esp the one with the two daughters and getting married so i can get the holy sword
Maybe you just had too much time away from TOEE and together with the overly-easy recent games Some random enemy crits can be frustrating on low-level parties, true. But, IIRC, Co8 actually made Lubash the Ogre easier in the Moathouse. In vanilla he used to be able to KO an entire party in one round - with his Great Cleave.