Thermal Jacket or just Waterproof?

Have you looked at Stolen Goat? Either the Orkaan LS jersey or if you want proper thermal the the Climb and Conquer jacket. I have the jacket. Warm, wind proof and waterproof yet a soft shell. Admittedly you'd not wear it in double figure temps. To give you an idea of performance of Stolen goat stuff. I've got castelli gear, Rapha gear, have used endura and have a provision 360 crs hard shell waterproof jacket for commuting. Went out today, overcast, 4 degrees plus windchill. Think it would make it hovering around zero. Had castelli thermal baselayer plus gabba jacket on top. Was cold with windchill across chest, but bibtight with nothing under them were Stolen Goat Orkaan. Legs warm throughout ride, no windchill at all and as an aside seat pad a 9/10 only because a Rapha pro team pad would be a 10 as its like sitting on a pillow. Next set of shorts I need I'll be getting them from SG.

As has been said above, waterproof like boil in a bag and you'll not want to use it. A great waterproof soft shell at a sensible price like Stolen Goat Climb and Conquer would be a reason to get on the bike even in Winter. They do climb and conquer bibtights for really cold weather too (on the way in post - can't wait)

Good luck

Hah! Funny, but I thought I was the only one with regard to rain jackets.  Bought a great Goretex active rain jacket but hardly ever use it and before that my other rain jacket only got used and handful of times in two years on the wettest of days.  Soft shells, gillets, arm warmers, base layers, L/S and S/S jerseys all mixed up see far more use.

I have a good waterproof and most of the time its hanging up in the house or rolled up in my back pocket. I've found ever since owning a Gabba (LS and SS) and an Alpha jacket which will take a shower, it has to be really heffing if down for the rain jacket to come out. In a similar sense to above:

Cold (<5 C): Castelli Alpha winter jacket with either a merino or synthetic baselayer depending on temperature. If below zero will often go merino vest under merino LS baselayer.

cool (<10): LS gabba with either synthetic baselayer, or 'skins' type if warmer. Thin merino if damp. 

If its really raining hard, then I'll sling the waterproof over the top of either option, but that does tend to get a bit sweaty if working hard as you have 2 membranes for the sweat to escape though. But it does stop you getting soaked and then chilled. 

If its biblical rain before leaving the house, its time for the turbo! 

Kind of depends what you have already.

Waterproof probably isnt as useful as a windproof in the winter - you'll be out in the wind more than the rain. 

Layers (what they all said) - good for thermal regulation...being wet isn't the end of the world

Cold/Dry Down to about 0 degrees

Thermal shorts and regular* bibtights along with Shimano Gore tex winter boots and merino socks

*or roubaix if windchill is more prevalent

Short sleeved Merino Base layer (sometimes 2 baselayers) & Acqua Zero Jersey/Jacket (Cervo Rosso Ibrido) (arm warmers under jersey)

Cold/Wet

Similar to above but substitute baselayer for a Rapha "waterproof" pro team softshell (but makes it kind of sweaty if travelling at pace in the 6-10 deg range), occasionally another short sleeve jersey under the long sleeve, I always carry a packable wind breaker for rest stops and or late afternoon/evening rides. If it's not too bad maybe just a windvest.

I have an Agu short sleeved softshell (cheap gabba) which I'll wear on warmer wet days.

I very rarely wear a full on waterproof jacket, these days...

I recently bought a Hoy Vulpine Fortress - it was looking like an ideal autumn short sleeve/armwarmer combo, but after wearing it only twice there appears to be a flaw in the pocket stitching and the material has developed a flaw with a striated type issue around the bar tacked stitching at the top of the pockets...so I currently would not recommend that particular jersey.

I also didn't get on with the length of the body on Gabba jerseys...next stop is maybe a Stolen Goat/Bioracer type...

Layers.  And next time when you are allowed, and if you feel you need it, the full winter jacket.  But layering is always more versatile.

Don't see the point in jackets unless it is raining moderate to heavy. To be honest i would not be out in rain if i can help it, sounds like you are the same. Yesterday it was dry and 4 degrees for most of the ride. My clothing choice was;

Standard Autumn/ Spring short sleeve base layer, arm warmers, short sleeve jersey, long sleeve jersey as outer layer and then a windstopper gilet. Liner gloves and thick outer gloves. I had good thermal tights on the bottom half.

As you note,multiple layers is best. I always double jersey in the winter as it means i have more pockets available to put arm warmers or liner gloves if i get really hot. Extra pockets are also good to carry a shower jacket if there is a chance of rain.

As it happens i have a good quality insulated rain jacket hanging up that came out once last winter and if i recall only twice the winter before!

My vote is for layering.

Having good waterproof footwear, a hat under your helmet and good gloves will keep you comfy even if you don't have the thickest most waterproof jacket.

I have a Giordana jacket, which does most things well. Minus degrees yesterday but used with a long sleeve base layer and a gilet was warm as toast. Took gilet off as the temperature rose. No bulk and whilst it keeps me dry in damp conditions, like seemingly every non hundreds of pounds jackets it is not waterproof and doesn't claim to be.