Thanks all for the replies! All very useful tips and not just for the one fight
Ishamael, you do not have to fight all of them at once. Position your party out in the room prior to cultists (the one with the orcs) and keep them out of sight of the door. Then advance a caster/archer into the room and do a snipe of the nearest cultist (the one in the middle left). This will pull them to you one at a time and through the bottleneck of the door. It takes time for them to advance & you can build a pool of AP first.
This did the trick! Thankyou very much

I guess I was too focused on having my rogue dish all the damage with madora soaking it - which lead to madora being smashed to bits and then my rogue haha. Positioning was definitely the key problem here ( Seems to be an issue I have in a few games lol.)
On a sidenote that is offtopic but I feel I shouldn't open up a new thread and start a war as its really just a yes/no I am after and nothing more, are rogues viable damage dealers for the rest of the game?
p.s 4verse have you figured out how to get there? If not leave a reply

I have had a few friends get stuck finding this as well!
Again, thanks for all the fast replies

- Ishamael