Stick a good 30 gallon trash bag in your pack and a length of paracord or a long belt. Cut the bottom out of the trash bag. In an emergency, you can make a skirt which will keep the upper legs dry. The lower legs won't matter much. In warmer weather, a 30 gallon bag makes a reasonable poncho as long as you don't move too fast and sweat under it.

My rain jacket is an essential part of my layering system, but people have different solutions. I have an REI version of the Precip.

Groups can be dicey and I find it best to stay in the follower role and keep my mouth shut. Personally, when I go out on a winter hike in most areas, I take a full pack. It may seem extreme, but a badly sprained ankle can quickly turn a day hike into an overnight trip. I usually avoid hiking groups because they always leave too late in the morning and there is always some inexperienced person to slow things down.

I'm not a member of the "cotton kills" club, as my backup plan if I see a wet and chilling situation coming is to set up the tent and get in the sleeping bag. It did happen to me once, and it wasn't a big deal. Sometimes I wear jeans or cotton cargo pants on winter hikes when it's too cold for the possibility of rain. I do carry cheap rain pants in case I need them to break the wind. I sometimes wear synthetic pants in the summer when it's hot, but I think this year, I'm going to switch to shorts. The thing about wearing cotton is a person has to grasp the necessity of staying dry from rain and from perspiration.

Maybe this is a situation where "Hike your own hike" applies.