Running 0.8 SV on Easy and then 0.7 on Normal gives me an idea of the mapper not knowing where he was aiming at. On a side note, the difference of rhythms isn't that noticeable either. Until 00:39:666 - the gap between Easy - Normal is actually pretty good but then it's like... playing an easier Normal.
Talking about Hard having 0.8 and Insane 1.6 SV isn't that much of a difference considering Hard contains some 1.4 SV green lines which helps a bit. Regarding rhythm, whilst Hard does not contain a single triplet nor a stream at all, triplets from Insane should be re-considered to balance the spread a bit and/or turning some streams into 1/4s. Notes such as 01:15:291 (5) - (on Insane) could (or should) be removed to make a healthier spread.