I have a Novara hi-vis rain shell. It had armpit zipped vents (can also remove the sleeves if I necessary). The shell keeps me from getting wet from the rain, but yeah, I can get pretty steamy inside and I end up wet from sweat. I think it works reasonably well. As for keeping my bottom half dry, I'd rather just wear bib shorts and let my legs get wet. My biggest concern is keeping my feet dry and for that I plan on buying booties.

If anyone has a good recommendation for rain pants that are breathable, my ears are open!