RW-1 : I have done alot of night approaches to verious kinds pf poorly lit helipads and I have experienced that same thing. You are on the approach every thing feels fine then all of a sudden in the last 1/4 mile it feels like you are over running the pad.This condition is much worse if you have a tail wind.
The method I prefer using is Altitude and Distance. Similiar to Off-shore Igor's technique but I use higher altitudes if flying to an on-shore helipad over rough terrain. I like 800 feet a mile back 400 to 500 feet half a mile back 200 to 300 feet a quarter mile back. Speed; slightly above VTOSS if multi-engine (50-to 60 knots)at the start of the approach.
At 1/4 mile back at 250 feet your airspeed should be slightly above translation and decelerating and don't forget POWER. From this point it is all visual and seat of the pants.
Best to try some of these approaches in day light to get the profile and then try it at night. Be really careful of long shallow approaches on black nights as you can end up flying into the ground (CFIT).
By the way : A continuous decent from 800 feet and 1 nm back to pad impact will result in a glide slope of approximately 7.5 degrees.