If it rains your going to get wet... period. I learnt this the hard way - I bought a Arcteryx Zeta AR for $800... I know ... Anyway do I stay dry? nope I get wet on the inside from sweat.
Your better off to go cheap and dirty as in a jacket with pit zips or something - hell, you could even buy a $20 yellow warehouse PVC jacket and cut your own pit zips
I find the navy blue PVC coated nylon Warehouse jackets are actually quite tough and robust and definitely waterproof. Still use one as a bushbashing jacket when I want to protect the other raincoat (Line 7 flexothane).
The major issues of the jacket are the short length (wet arse) and the packaway hood has poor visibility (wear a visor/cap underneath). I sweat a lot so I also have rivers of sweat draining out of the sleeves and back...
warehouse sell 2 pvc jackets. The yellow one is stiff and heavy Havnt tried one. The blue one is what I used to use untill I got a real coat and the pvc got thrown in the 4wd. The zips starting to fray probably due to being under the working end of a spade.
That flexothane is weired stuff. Those that have then swear by them in much the same way as Aarn pack users. Its meant to be breathable but since the surface has no repellent I cant see how
Years ago I had a Warehouse yellow PVC jacket which was bomb, and water, proof. Used it for thrashing around our land in the bush and it never leaked. Eventually it expired and I bought another but, low and behold, the new one was crap. Bought a more expensive one from Rural Service Center - also crap, seams went in a jiffy.
As I've got older I've worked out that the best way to not get wet when tramping is to not go when it looks like rain!