Flemeth: 1 melee to distract her, everybody else use ranged attacks; bring a healer
High Dragon: moves around a lot; use a tank and a DPS and two ranged attackers (preferably one a healer). Ranger summons are good to distract the dragon. Don't use fire attacks - it is immune to them. Pause often and heal whoever is banged up or else set Tactics to take a poultice whenever <50% health. Shale cannot be grabbed - good choice for tank. If you have an Assassin in the party, use Death Mark to grant everyone critical hits.
The forums are kinda slowish about showing everything everywhere. My favorite is when someone makes a new post in a thread I've been following, but when I click over to go to that thread said post isn't there for five minutes.
Anyway, I've found the easiest way to kill the high dragon on the peak is alternating CoC mages, at least one of which has forcefield as a back up incase the dragon grabs someone while both CoCs are on cool down.
Just be careful that your mages don't get into firebreath or melee/slap range.
killed the high dragon so next is flemeth Oghren surprising is my go to tank so i think i bring wynne for arcane support then i thought Lin for archery or Shale