I must get it right about 4/5 of the time I fly into LGW- twice a day. However, though we have very primitive nav kit, we do have a copy of the booklet LGW sent us with the tables in. That certainly helps, as does the ability of the 146 to steepen it's descent if you get it wrong.
I often have to fly about 2-300fpm to stay sensible, but If I've got the ones that allow it, I can set up a couple of mythical base leg and long final points and give them a vertical gate to help- that's with a GNS-XLS as well, not a fancy modern FMS. Just using every tool in the box to help.
Obviously an FMS based approach would help, but sometimes you get silly long downwind legs to alter spacing for departures that bugger up any hope of getting it right. Not our fault but does that affect the published stats?