I have discovered a most imbalanced tactic that works very well in these situations. I even managed to clear out the massive pack with double spellcasters and two Fampyrs on the Adra hand, despite the fact that my group is only five level 6 characters (and Kana is ... not tremendously useful).
The basic essence of this is the level 1 Priest spell, Withdraw. For some reason, Withdrawn characters (which are immune to basically all statuses and damage) actually still block pathing. Therefore, to get a free win, place the most useless or most tanky member of your party where they will block the entryway. Then cast Withdraw on them. It lasts a whole 28 seconds and as just a level 1 spell, Durance can easily cast it several times, blocking up the entryway from your enemies for just about two whole minutes. All you have to do is pay attention to the Withdraw timer and then cast Withdraw on them immediately. The enemy will not be able to get through unless they can clean up your chosen meatshield in (literally) about two seconds or less, and the meatshield will be on 100% Endurance every time because he recovers Endurance whilst Withdrawn.
In this time, you can easily get your party wizards to AoE the crap out of whoever's on the other side. Bonus: You can't hit your Withdrawn character, so you can cast AoE damage effects with no regard.
For the fight on the Adra hand, I lured my enemies over the bridge. This meant that I could keep my casters well out of their spell range, and lob line-of-effect spells like Lightning Bolt and Ball of Fire to hit basically every enemy on the bridge. This would have been substantially more successful on normal terrain but it seems that it's actually pretty difficult to hit enemies on the bridge, even if they're blatantly in the line of fire, so you have to practice a bit before you can actually hit them.
This is why I play the game for my first time on the "Infinity Engine expert" difficulty.