DKs can solo most of it. Gunship and Valithria haven't been gotten on 25H yet, but thus far there's nothing major stopping DKs from getting them. Next tier at the latest.
So I suppose you only really need 2 then to full clear for sure. --- One day dude, I'm just gonna get off the bus, and I'm gonna run in the woods and never come back, and when I come back I'm gonna be the knife master! -The Rev
5 and a healer at least since I don't know the skill/gear level of your guildmates. It CAN be done with less, it MIGHT take you more, who knows. Good rule of thumb is 'if you can't do it, throw more 90s at it'. Make sure you have a healer, though, for valith at least. --- IMO