Pics would help us understand your situation, but generally you don't want large pains of glass everywhere allowing players to see a lot of stuff at once.
Solid walls and geometry is your primary form of optimisation. Well considered corners and wall placement. Then you have your areaportals and hints which both reduce vvis's tendancy to make bad visleaf formations and cull render loads by reducing the rendering of faces in unseen areas of the map. Hints are passive whilst areaportals are active methods of doing so. Hints arn't as significant in tight indoors quarters anymore as areaportals should be placed in most doorways and windows, but deffinately have a place in larger out doors areas.
Since your map sounds like it's indoors func_visclusters probably wont be of much use, they are primarily for reducing compile times by telling vvis to skip math calculations of certain visibility in x portal leafs, but might have a side effect of more efficient rendering in large open areas in said leafs. I managed to reduce a map's compile time by a third by introducing these babies into 3 of 5 areas of a cp map of mine.
If you have a lot of windows and similarly sized rooms you might get away with a medium distance but sudden min-max fog setting/max clipping plane. That would at least increase in game performance, although the fog wont do much for compile times the max clipping plane might.
Occluders wont really help compile times.
