I am not sure if that will be useful but since I have them, here are the profils using gprof for writing a 1000x2560x2560 dataset using direct chunk, hyperslab chunk and hyperslab contiguous.
profile_hslab_contig.txt (481.2 KB)
profile_hslab_chunk.txt (485.5 KB)
profile_direct_chunk.txt (475.2 KB)