I agree with most here, atm we dont have alot of either so I won't use todays XIV as an example, but to give a rough % number I'd say 60-70open/40-30instanced would feel like the perfect balance for me.

Beastmen strongholds and world bosses/HNM are great and I like to see more of them, but I'd also like to see more varied instanced content such as instanced boss fights(BCNM, primal fights, story and gc missions etc) as well as both big and small dungeon crawls (prerebly not as linear as darkhold).