The Poncho and the light showerproof jacket underneath is the solution that I've arrived at as well. My reasons for doing so is that rain doesn't tend to happen every day and of course, 'rain' can be anything from drizzle to heavy downpours, short or long in duration, and with or without various wind speeds to make it easy to cope with, or to feel overwhelmed by it.
So from a drizzle situation to a certain point in personal decision making, a single skin jacket like the Marmot Precip (I used to own one) is maybe a base starting point for when the rain is 'easy' to live with, to the need for greater protection when the rain becomes hard to bear, it's then that a completely waterproof poncho can really help.
In my particular case, I already own a Rab Vital jacket which is OK for a short while in drizzle so I'm now aiming to buy a lightweight waterproof running type jacket for the next stage of rain and then use my poncho as my final barrier against getting wet.
At this very moment, my wife's friend is adapting my Vaude poncho and is fitting a full zip to it, from chin to hem, I'm hoping that it works, if not I'll buy a different brand, either the Decathlon poncho or the Altus model. Both of these have full zips as part of their design.
It's only the lightweight waterproof jacket choice that continues to cause me problems. I've decided that I'm not going to buy another Marmot Precip so I'm down to an Alpkit Gravitas, a Rab Kinetic Plus (the older model) or a Rab Kinetic Alpine (the latest model) and I'm considering a couple of other brands as well. The particular problem that I can't seem to solve is they all come with hoods, how many more hoods do I need in my life???
It may seem odd to be planning on three items of clothing to deal with rain but my experience tells me that one waterproof jacket is not the overall answer to all of the types of rain that I've been subjected to. And interestingly, when added together my three items are about the same weight as my Paramo Alta 2, and (except for the poncho) when folded up and not in use they take up less space in my rucksack. And another consideration for me is that the items I'll use can be used for other situations as well, wind protection, a groundsheet, and so on.
My quest to find my perfect answer to rain goes on.