You can get up in the rafters and kill Ragzlin sometimes its super easy other times things can go pear shaped,
Agreed.
If you’ve recruited Lump then you can also call the ogres for the fight with Ragzlin, but due to limited room they don’t always appear in a useful place. If you can speak with animals, you might be able to persuade the spiders in the pit to attack the goblins too - they will tend to go for Ragzlin’s room I think after dealing with the closest guards. They won’t last long by themselves, but can provide a distraction.
Also look out for the enemies with low HP and pick these off first, so there are fewer to deal damage in return. There are a number of these in Ragzlin’s room, so with some luck you can very quickly reduce the number of enemies you’re dealing with.
Another possibility is to keep your party in or near the library on the way to where you found Minthara after she and the nearby goblins are dead. Then send someone with a good ranged attack to snipe through the broken wall to Ragzlin’s room to start the fight. If the door nearest the library is still locked, then the enemies will tend to come the long way round, giving you chance to damage them from range before they get to you and generally not have to deal with them all at once. If you have an area of effect spell like Cloud of Daggers or just a fire surface or two, forcing enemies to come to you through them will mean they lose HP on the way. (Be wary of pulling other goblins from the main room into this fight, though, if you have it outside Ragzlin’s room.)