The first floor (beach) is indeed a bit linear, however that will gradually change when you reach the lower floors. There is a lot of open ground on the first area but there are still 3 approaches you can take. However since 1 is completely suicidal and another is class specific, only the easiest of the 3 is used which encourages linearity a bit.

There is always the danger of ruining difficulty if you allow too many approaches because then you have to make some areas more inviting (=easier).

Ah, so you were the map creator too! From what we played together (first two floors, ish...), I see what you are going for with the level (suspected it while playing, confirmed reading the description).

My main thought is that it has some vicious chokepoints. It makes it a bit like there's a strong linear progression between tasks. When we split up, it was mostly because some people we tackling something while others decided to explore ahead. Most official maps presented at least two path options in every situation, such that A-team and B-team could avoid each other right up until the stairs. It's very interesting seeing your map diverge (heh) somewhat from that.

I'm a speedrunner at heart, so your map sure forces a change of pace for me! Nice job finding a niche the official maps don't quite fill.